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ukssdc_d.bib
@comment{{This file has been generated by bib2bib 1.93}}
@comment{{Command line: /soft/ukssdc/share/bib2bib -c 'exists ukssdc_d' -s author -ob ukssdc_d.bib ukssdc.bib}}
@article{altadill2003:_time_scale,
author = {Altadill, D. and Apostolov, E.M.},
title = {Time and scale size of planetary wave signatures in the
ionospheric F region: Role of the geomagnetic activity and
mesosphere/lower thermosphere winds},
journal = {Journal of Geophysical Research},
year = {2003},
volume = {108},
number = {A11},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2003JA010015},
abstract = {The time and scale size of planetary wave signatures (PWS)
in the mid latitude F region ionosphere of the Northern
Hemisphere and the main pattern of their possible sources of
origin are presented. The PWS involved in this study have
periods of about 2-3, 5-6, 10, 13.5, and 16 days. The PWS in
the ionosphere are large scale phenomena. PWS with periods
of about 2-3 and 5-6 days have a typical longitudinal size
of $80^{\circ}$, they are coherent some 6000 km apart, and
they occur about 12\% and 14\% of the entire observational
record respectively. The typical longitudinal size of PWS
with periods of about 10 and 13 days is $100^{\circ}$, they
are coherent some 7500 km apart, and they occur about 24\%
and 22\% of the entire observational record respectively. PWS
with periods of about 16 days seem to be global scale
phenomena, and they occur about 30\% of the entire
observational record. The results estimate that geomagnetic
activity variations play the most important role for driving
PWS in the ionosphere. The geomagnetic activity variations
can drive at least 20-30\% of the PWS with periods of about
2-3, 5-6, 10 and 16 days, but even up to 65-70\% for the PWS
with periods of about 10 and 16 days, and they practically
drive 100\% of the PWS with periods of about 13.5 days. The
planetary wave activity in the mesosphere/lower thermosphere
(MLT) winds can drive about 20-30\% of the PWS with periods
of about 2-3, 5-6, 10 and 16 days. There is a significant
percentage of existence of PWS in the F region apparently
'independent' from the geomagnetic activity variations and
of the MLT winds. The latter is better expressed for PWS
with shorter period. PWS with periods of about 13.5 days are
an exception to that. A candidate mechanism for the
'independent' events may be the non linear interaction or
the amplitude modulation between different PWS.}
}
@article{altadill2003,
author = {Altadill, D. and Apostolov, E.M. and Jacobi, C. and
Mitchell, N.J.},
title = {Six-day westward propagating wave in the maximum electron
density of the ionosphere},
journal = {Annales Geophysicae},
year = {2003},
volume = {21},
number = {7},
pages = {1577--1588},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
abstract = {Analyses of time-spatial variations of critical plasma
frequency foF2 during the summer of 1998 reveal the
existence of an oscillation activity with attributes of a
6-day westward propagating wave. This event manifests itself
as a global scale wave in the foF2 of the Northern
Hemisphere, having a zonal wave number 2. This event
coincides with a 6-day oscillation activity in the
meridional neutral winds of the mesosphere/lower
thermosphere (MLT). The oscillation in neutral winds seems
to be linked to the 6-7-day global scale unstable mode
westward propagating wave number I in the MLT. The forcing
mechanisms of the 6-day wave event in the ionosphere from
the wave activity in the MLT are discussed.}
}
@article{altadill2001,
author = {Altadill, D. and Gauthier, F. and Vila, P. and Sole,
J.G. and Miro, G. and Berranger, R.},
title = {The 11.08.1999 solar eclipse and the ionosphere: a search
for the distant bow-wave},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2001},
volume = {63},
number = {9},
pages = {925--930},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The advantage of studying eclipse disturbances is the
perfect predictability of their 4D source geometry, which
allows for preparation of adapted systems and schedules. The
total solar eclipse period of August 11, 1999 across Europe
was notable for exceptionally uniform solar disk, steady
solar wind and quiet magnetospheric conditions. Large-scale
gravity wave activity prior to the eclipse however disturbed
the initial 0900 LT thermosphere weather. This rapid letter
is an advance summary about one particular aspect of the
West European ionosonde and radar results of the eclipse
experiment. It focusses on the possible emergence of a
distant eclipse frontal bow-wave. This was expected as a
consequence of the supersonic shock of stratospheric Ozone
cooling. First-look data of Vertical Incidence Digisonde
records are greatly improved by their Real-Time acquisition
of inverted true-height profiles. The EBRE (Tortosa, Spain)
foF1 and foF2 simultaneous oscillations observed from the
second to the fourth hour following maximum solar
occultation appear as convincing indicators of the bow-wave
signature. Large fluctuations in foF1 and foF2 during some
of our control days, of usual gravity wave character,
emphasize the importance of meteorologic disturbances on
mid-latitude ionosphere variability.}
}
@article{altinay97:_forec,
author = {Altinay, O. and Tulunay, E. and Tulunay, Y.K.},
title = {Forecasting of ionospheric critical frequency using neural
networks},
journal = {Geophysical Research Letters},
pages = {1467--1470},
year = {1997},
month = jun,
volume = {24},
number = {12},
abstract = {Multilayer perceptron type neural networks (NN) are employed
for forecasting ionospheric critical frequency (foF2) one
hour in advance. The nonlinear black-box modeling approach
in system identification is used. The main contributions:
1. A flexible and easily accessible training database
capable of handling extensive physical data is prepared,
2. Novel NN design and experimentation software is
developed, 3. A training strategy is adopted in order to
significantly enhance the generalization or extrapolation
ability of NNs, 4. A method is developed for determining the
relative significances (RS) of NN inputs in terms of mapping
capability.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{apostolov04,
author = {Apostolov, E. M. and Altadill, D. and Todorova, M.},
title = {The 22-cycle in the geomagnetic 27-day recurrences
reflecting on the F2-layer ionization},
journal = {Annales Geophysicae},
pages = {1171-1176},
year = {2004},
volume = {22},
number = {4},
abstract = {Solar cycle variations of the amplitudes of the 27-day solar
rotation period reflected in the geomagnetic activity index
Ap, solar radio flux F10.7cm and critical frequency foF2 for
mid-latitude ionosonde station Moscow from the maximum of
sunspot cycle 18 to the maximum of cycle 23 are
examined. The analysis shows that there are distinct
enhancements of the 27-day amplitudes for foF2 and Ap in the
late declining phase of each solar cycle while the
amplitudes for F10.7cm decrease gradually, and the foF2 and
$A_{p}$ amplitude peaks are much larger for even-numbered
solar cycles than for the odd ones. Additionally, we found
the same even-high and odd-low pattern of foF2 for other
mid-latitude ionosonde stations in Northern and Southern
Hemispheres. This property suggests that there exists a
22-year cycle in the F2-layer variability coupled with the
22-year cycle in the 27-day recurrence of geomagnetic
activity.},
ukssdc_d = {}
}
@article{araujo-pradere01:_evaluat_storm_time_ionos_empir,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J.},
title = {Evaluation of the STORM Time Ionospheric Empirical Model for
the Bastille Day event},
journal = {Solar Physics},
pages = {317--324},
year = {2001},
month = {Dec},
volume = {204},
number = {1-2},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Recent theoretical model simulations of the ionosphere
response to geomagnetic storms have provided the
understanding for the development of an emperical storm-time
ionospheric model (STORM). The emperical model is driven by
the previous time-history of $a_{p}$, and is designed to
scale the quiet-time F-layer critical frequency
($f_{o}F_{2}$) to account for storm-time changes in the
ionosphere. The model provides a useful, yet simple tool for
modeling of the perturbed ionosphere. The quality of the
model prediction has been evaluated by comparing with the
observed ionospheric response during the Bastille Day (July
2000)storm. With a maximum negative $D_{st}$ of -290 nT and
an $a_{p}$ of 400, this magnetic perturbation was the
strongest of year 2000. For these conditions, the model
output was compared with the actual ionospheric response
from all available stations, providing a reasonable
latitudinal and longitudinal coverage. The comparisons show
that the model captures the decreases in electron density
particularly well in the northern summer hemisphere. In
winter, the observed ionospheric response was more variable,
showing a less consistent response, imposing a more severe
challenge to the emperical model. The value of the model has
been quantified by comparing the root mean square error
(RMSE) of the STORM predictions with the monthly mean. The
results of this study illustrate that the STORM model
reduces the RSME at the peak of the disturbance from 0.36 to
0.22, a significant improvement over climatology.}
}
@article{araujo-pradere2003,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J. and Bilitza,
D.},
title = {Validation of the STORM response in IRI2000},
journal = {Journal of Geophysical Research},
year = {2003},
volume = {108},
number = {A3},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2002JA009720},
abstract = {[1] The latest version of the International reference
ionosphere, IRI2000 [Bilitza, 2001], contains a dependence
on geomagnetic activity based on an empirical storm-time
ionospheric correction model (STORM) [Araujo-Pradere et al.,
2002]. The new storm correction in IRI is driven by the
previous time history (33 hours) of $a_{p}$ and is designed
to scale the normal quiet-time F layer critical frequency
($f_{o}F_{2}$) to account for storm-time changes in the
ionosphere. An extensive validation of IRI2000 has been
performed during geomagnetic storm conditions to determine
the validity of the new algorithms. The quality of the
storm-time correction has been evaluated by comparing the
model with the observed ionospheric response during all the
geomagnetic storms with $a_{p}>150$ in 2000 and 2001, a
total of 14 intervals. The model output was compared with
the actual ionospheric response for all available ionosonde
stations for each storm. The comparisons show that the model
captures the decreases in electron density particularly well
in summer and equinox conditions. To quantify the
improvement in IRI2000, the root-mean-square error has been
evaluated and compared with the previous version of IRI,
which had no geomagnetic dependence. The results indicate
that IRI2000 has almost a 30\% improvement over IRI95 during
the storm days and is able to capture more than 50\% of the
increase in variability, above quiet times, due to the
storms.}
}
@article{araujo-pradere2005,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J. and Bilitza,
D.},
title = {Time Empirical Ionospheric Correction Model (STORM) response
in IRI2000 and challenges for empirical modeling in the
future},
journal = {Radio Science},
year = {2004},
volume = {39},
number = {1},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2002RS002805},
abstract = {IRI2000 [Bilitza, 2001] now contains a geomagnetic activity
dependence based on the Time Empirical Ionospheric
Correction Model (STORM) [Araujo-Pradere and Fuller-Rowell,
2002; Araujo-Pradere et al., 2002]. The storm correction is
driven by the previous time history of $a_{p}$ and is
designed to scale the quiet time F layer critical frequency
($f_{o}F_{2}$) to account for storm-time changes in the
ionosphere. The quality of the storm-time correction was
recently evaluated by comparing the model with the observed
ionospheric response during all the significant geomagnetic
storms in 2000 and 2001. The model output was compared with
the actual ionospheric response at 15 stations for each
storm. These quantitative comparisons using statistical
metrics showed that the model captures the decreases in
electron density particularly well in summer and equinox
conditions, but is not so good during winter conditions. To
further assess the capabilities of the model, STORM has been
compared in detail with observations during the Bastille Day
storm in July 2000. This storm, considered to be on the
extreme end of the statistical scale of storm magnitude,
highlights two main areas were challenges remain for the
empirical storm-time ionospheric model. The first is the
rapid onset of the positive storm phase; the second is the
regional composition changes that can affect one longitude
sector at the expense of another for a particular
storm. Both these challenges, although appreciated during
the development of STORM, remain to be addressed.}
}
@article{araujo-pradere02:_storm1,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J. and Codrescu,
M.V.},
title = {STORM: An empirical storm-time ionospheric correction model
- 1. Model description},
journal = {Radio Science},
year = {2002},
month = {Sept},
volume = {37},
number = {5},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2001RS002467},
abstract = {Using data from 75 ionosonde stations and 43 storms, and
based on the knowledge gained from simulations from a
physically based model, we have developed an emperical
ionospheric storm-time correction model. The model is
designed to scale the quiettime F region critical frequency
($f_{o}F_{2}$) to account for storm-time changes in the
ionosphere. The model is driven by a new index based on the
integral of the $a_{p}$ index over the previous 33 hours
weighted by a filter obtained by the method of singular
value decomposition. Ionospheric data was stored as a
function of season and latitude and by intensity of of the
storm, to obtain the corresponding dependencies. The good
fit to data at midlatitudes for storms during summer and
equinox enable a reliable correction, but during winter and
near the equator, the model does not improve significantly
on the quiet time International Reference Ionosphere
predictions. This model is now included in the international
recommended standard IRI2000[Bilitza 2001] as a correction
factor for perturbed conditions.}
}
@article{araujo-pradere02:_storm2,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J. and Codrescu,
M.V.},
title = {STORM: An empirical storm-time ionospheric correction model
- 2. Validation},
journal = {Radio Science},
year = {2002},
month = {Sept},
volume = {37},
number = {5},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2002RS002620},
abstract = {[1] STORM is an empirical ionospheric correction model
designed to capture the changes in F region electron density
during geomagnetic storms. The model is driven by the
previous 33 hours of $a_{p}$, and the output is used to
scale the quiet time F region critical frequency
($f_{o}F_{2}$) to account for increases or decreases in
electron density resulting from a storm. The model provides
a simple tool for modeling the perturbed ionosphere. The
quality of the model has been evaluated by comparing the
predictions of the model with the observed ionospheric
response during the six storms in the year 2000. The model
output has been compared with the actual ionospheric
response at 15 ionosonde stations for each storm. The
comparisons show that the model captures the decreases in
electron density particularly well in summer and equinox at
midlatitudes and high latitudes but is less accurate in
winter. The value of the model has been quantified by
comparing the daily root mean square error of the STORM
predictions with the monthly mean. The results of the
validation show that there is a 33\% improvement of the STORM
model predictions over the monthly median during the storm
days and that the model captures more than half of the
increase in variability on the storm days, a significant
advance over climatology.}
}
@article{araujo-pradere2005:_variability,
author = {Araujo-Pradere, E.A. and Fuller-Rowell, T.J. and Codrescu,
M.V.},
title = {Characteristics of the ionospheric variability as a function
of season, latitude, local time, and geomagnetic activity},
journal = {Radio Science},
year = {2005},
volume = {40},
number = {5},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2004RS003179},
abstract = {An ionospheric $F_{2}$ critical frequency database has been
assembled to determine the variability of the $F$ region as
a function of local time, latitude, season, and geomagnetic
activity. The database comprises observations from 75
ionosonde stations covering a range of geomagnetic latitude
and includes 43 storm intervals. The database was previously
used to develop the Storm-Time Empirical Ionospheric
Correction Model (STORM). The mean and standard deviation
have been evaluated by sorting the data by local time,
season (five intervals centered on equinox, solstice, and
intermediate intervals), latitude (four regions each
$20^{\circ}$ wide in geomagnetic latitude), and up to eight
levels of geomagnetic activity. The geomagnetic activity
index was based on a weighted integral of the previous 33
hours of ap and is the same as that used by the STORM
model. The database covers a full solar cycle, but
insufficient information was available to sort by solar
activity without compromising the estimates of variability
on the other sorting parameters. About half the data were
contained in the first level of geomagnetic activity,
between 0 and 500 units of filtered $ap$ corresponding to
$K_{p} <= 2$, and half above that level. When local time
dependence was included in the binning, sufficient data were
available to sort into two levels of geomagnetic activity,
quiet ($K_{p} <= 2^{+}$) and disturbed ($K_{p} >
3^{-}$). For all latitudes and levels of geomagnetic
activity, the lowest variability was typically found in
summer (10-15\%), and the largest variability occurred in
winter (15-40\%), with equinox (10-30\%) lying between the
solstice extremes. The exception was low latitudes at
equinox, which had surprising low variability (10\%),
possibly because of the weak interhemispheric flow at this
time of year. At middle and low latitudes, the variability
tended to increase with geomagnetic activity in winter and
equinox but remained fairly constant in summer. At high
latitudes, the surprising result was that in all seasons,
and in winter in particular, the variability tended to
decrease, probably because of the increased upwelling of
neutral molecular species and stronger chemical control of
the ionosphere. The data have also been used to build a
table of estimated variability suitable for inclusion in the
International Reference Ionosphere or any other
climatological model. For periods where data were scarce or
nonexistent, an estimated variability was provided on the
basis of expectations of the consequences o physical
processes. This was necessary to fill in the table o values
in order to develop a module suitable for inclusion in th
International Reference Ionosphere.}
}
@article{aruliah1996,
author = {Aruliah, A.L. and Farmer, A.D. and Fuller-Rowell, T.J. and
Wild, M.N. and Hapgood, M. and Rees, D.},
title = {An equinoctial asymmetry in the high-latitude thermosphere
and ionosphere},
journal = {Journal of Geophysical Research},
pages = {15713--15722},
year = {1996},
month = jul,
volume = {101},
number = {A7},
abstract = {A large equinoctial asymmetry has been observed in
thermospheric winds and ion velocities at high latitude
sites in northern Scandinavia. Throughout the solar cycle,
average nighttime thermospheric meridional winds are larger
in spring than autumn despite similar levels of solar
insolation. The average ion velocities are also larger in
spring than autumn at solar maximum, but at solar minimum
this position is reversed. Numerical simulations of the
thermosphere and ionosphere have not predicted such
asymmetries because they generally assume forcing functions
that are symmetric about the solstices. The proposed
explanation lies in the annual and diurnal variation in
solar wind-magnetosphere coupling caused by changes in the
orientation of the geomagnetic pole, and hence the
magnetosphere, with respect to the average orientation of
the IMF (the Russell-McPherron effect). This causes a
12-hour phase difference between the times of maximum solar
wind-magnetosphere coupling at the two equinoxes. In
addition, the orientation of the geomagnetic axis with
respect to the average IMF is such that $ > 0$
for the March equinox and $ < 0$ for
September. This results in a further source of asymmetry of
forcing of the high-latitude ionosphere as the result of
electric fields associated with the four sign combinations
of $B_{y}$ and $B_{z}$. Several predictions arise from the
explanation given: for example, a high-latitude station
measuring thermospheric neutral winds in Alaska,
$180^{\circ}$ in longitude from Kiruna, might be expected to
see nighttime thermospheric winds that are larger in the
autumn than in the spring.},
url = {http://www.agu.org/pubs/crossref/1996/95JA01102.shtml},
ukssdc_w = {},
ukssdc_d = {}
}
@article{aruliah97:_model_high_latit_equin_asymm,
author = {Aruliah, A.L. and Schoendorf, J. and Aylward, A.D. and Wild,
M.N.},
title = {Modelling the High-Latitude Equinoctial Asymmetry},
journal = {Journal of Geophysical Research},
pages = {27207--27216},
year = {1997},
volume = {102},
number = {A12},
abstract = {Fabry-Perot Interferometer measurements of neutral winds and
European Incoherent SCATter radar measurements of plasma
velocities have shown a significant equinoctial asymmetry in
the average behavior of the thermosphere and ionosphere
above northern Scandinavia. Existing standard models of the
upper atmosphere use forcing functions that are symmetric
about the solstices, therefore these observations are
unexpected. It is suggested that the asymmetry arises from
the diurnal variation in the cross polar cap potential
difference (CPCPD) because there is a 12 hour phase
difference between the variations at the March and September
equinoxes. The variation in the CPCPD is caused by an annual
and diurnal variation in the orientation of the
magnetosphere with respect to the interplanetary magnetic
field. This is known as the Russell-McPherron(R-M)
effect. The plausibility of this explanation of the
equinoctial asymmetry in thermospheric winds is supported by
investigation of the effect of their geomagnetic history,
i.e., the repercussions on the winds of the activity levels
in the few hours prior to the observation. The consequences
of the R-M effect have been simulated in the University
College London/Sheffield/Space Environment Laboratory
coupled thermosphere-ionosphere model by imposing a
diurnally varying high-latitude electric field pattern. The
results are used to test the predictions, given in an
earlier paper, of the average behavior expected at other
high-latitude sites. A corollary to the study is that the
evidence presented here implies that the auroral oval may be
smaller at solar minimum, which is also unexpected.},
ukssdc_w = {},
ukssdc_d = {}
}
@inproceedings{austin00:_near_vertic_incid_skywav_world_war_ii,
author = {Austin, B.A.},
title = {Near Vertical Incidence Skywaves in World War II: an
historical perspective},
booktitle = {IEE Conf. on HF Radio Systems and Techniques},
pages = {225--229},
year = {2000},
volume = {474},
ukssdc_d = {},
uk_first = {}
}
@article{austin:_whatever_happened_to_40_metres,
author = {Austin, B.A.},
title = {Whatever Happened to 40 Metres?},
journal = {Mercury, the Journal of the Royal Signals Amateur Radio
Society},
year = {2005},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{balthazor01,
author = {Balthazor, R.~L. and Denton, M.~H. and Pryse, E. and
Kersley, L. and Walker, I.~K. and Moffett, R.~J.},
title = {The morphology of the dayside ionospheric trough and the
nightside stagnation region: a coupled study},
journal = {AGU Fall Meeting Abstracts},
year = 2001,
month = dec,
pages = {A690+},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001AGUFMSA32A0690B&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {The Aberystwyth tomographic imaging experiment and the
Sheffield Coupled Thermosphere-Ionosphere-Plasmasphere model
(SCTIP) have been used to investigate the dayside
ionospheric trough at high latitude under different
geomagnetic conditions. Previous work has suggested that the
latitude of the trough minimum and the structure of the
poleward wall is dependent on the electron precipitation,
whereas the formation of the trough itself is dependent on
the convection of flux tubes. We further discuss the roles
of flux tube convection and the nightside stagnation region
in the formation of both the dayside and nightside troughs,
and the role of partially depleted flux tubes in the
observed equatorward structuring of the trough region.},
ukssdc_d = {},
uk_first = {}
}
@article{balthazor03:_trans_heatin_effec_auror_therm,
author = {Balthazor, R.~L. and Wilford, C. and Thom, S. and
Denton, M.~H. and Pryse, E.},
title = {Transonic Heating Effects in the Auroral Thermosphere},
journal = {AGU Fall Meeting Abstracts},
year = 2003,
month = dec,
pages = {A105+},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003AGUFMSA22A0105B&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {We review substantial recent developments to the CTIP
coupled thermosphere-ionosphere-plasmasphere model, using
observations from the Aberystwyth ionospheric tomographic
imaging chain and the IMAGE satellite to benchmark and
validate the model results. Thermospheric heating in auroral
regions has classically been viewed as a combination of
Joule Heating (macroscopic frictional heating from the
ionosphere), Lorentz forcing (microscopic momentum transfer
from ions) and particle precipitation. Of these, it has been
shown that above about 110 km, Joule Heating is the dominant
energy transfer mechanism. However, ion velocities during
disturbed times often approach or exceed the neutral sound
speed. We investigate shock front heating through modelling
using the improved CTIP model and compare these with in-situ
satellite observation. We conclude that shock heating may be
a significant contribution to the auroral
thermosphere-ionosphere energy balance.}
}
@article{bamford2001,
author = {Bamford, R.A.},
title = {The effect of the 1999 total solar eclipse on the
ionosphere},
journal = {Physics and Chemistry of the Earth - C},
year = {2001},
volume = {26},
number = {5},
pages = {373--377},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {The localised "night" created as the moon's shadow travelled
across the Earth during the total solar eclipse of 11th
August 1999, produced changes in the ionosphere across
Europe that were monitored with a variety of modern
instrumentation. The passage of the 100km wide, super-sonic
lunar shadow offered the opportunity to examine the changes
in electron densities, radio absorption, neutral wind
patterns and the possible generation of waves in the layers
of the ionosphere. All these for an event for which the
cause of the disturbance can be calculated with
accuracy. Reported here are the results from the vertical
ionosondes located under the path of totality and in the
partial eclipse region and dual frequency GPS TEC
measurements. The ionosondes showed that even in the partial
shadow the peak electron densities of the F & E ionospheric
layers decreased by as much as 20-35\%. The TEC measurements
showed that the vertical equivalent line integrated electron
density dropped by 15\% at the 97\% partial eclipse north of
the path of totality. The consequences of these observations
are discussed in relation to making model predictions.}
}
@article{belahaki2005,
author = {Belehaki, A. and Cander, Lj. and Zolesi, B. and Bremer,
J. and Juren, C. and Stanislawska, I. and Dialetis, D. and
Hatzopoulos, M.},
title = {DIAS Project: The establishment of a European digital upper
atmosphere server},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2005},
volume = {67},
number = {12},
pages = {1092--1099},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
abstract = {The main objective of DIAS (European Digital Upper
Atmosphere Server) project is to develop a pan-European
digital data collection on the state of the upper
atmosphere, based on real-time information and historical
data collections provided by most operating ionospheric
stations in Europe. A DIAS system will distribute
information required by various groups of users for the
specification of upper atmospheric conditions over Europe
suitable for nowcasting and forecasting purposes. The
successful operation of the DIAS system will lead to the
development of new European added-value products and
services, to the effective use of observational data in
operational applications and consequently to the expansion
of the relevant European market.},
keywords = {Ionosphere; Upper atmosphere; Ionospheric monitoring;
Ionospheric nowcasting; Ionospheric forecasting; Digital
libraries},
url = {http://dx.doi.org/10.1016/j.jastp.2005.02.021}
}
@article{belehaki02,
author = {Belehaki, A. and Tsagouri, I.},
title = {On the occurrence of storm-induced nighttime ionization
enhancements at ionospheric middle latitudes},
journal = {Journal of Geophysical Research},
pages = {1209},
year = {2002},
volume = {107},
number = {A8},
abstract = {Ionospheric observations from nine middle-latitude stations
are studied for five magnetic storms that occurred during
September and October 2000. The correlation between various
solar wind, magnetospheric and ionospheric parameters shows
that the nighttime ionospheric response is strongly
dependent on the conditions during which solar
wind-magnetosphere coupling occurred. Storms with initial
compressive phase and rapidly evolving main phase have as a
global effect the ionization depletion in the nightside at
middle latitudes, independent of the storm intensity. These
storms are caused by the abrupt dissipation of a large
amount of energy input, resulting in the rapid expansion of
the neutral composition disturbance zone equatorward,
producing the observed negative effects in all middle
latitude stations presented here. Gradually evolving
geomagnetic storms, driven by slowing increasing southward
IMF, result in the observation of positive effects at night
in low to middle latitude stations. The weaker the intensity
of the storm is, according to the Dst index, the more likely
it is that one will observe nighttime ionization
enhancements in subauroral latitudes as well. There are two
competing mechanisms causing the observed effects; the
expansion of the neutral composition disturbance zone
results in negative effects, while downward plasmaspheric
fluxes produce ionization enhancements at night. Gradually
evolving storms are characterized by the restricted
development of the neutral composition disturbance zone to
higher latitudes, and the extent of its equatorward boundary
depends on the intensity of the storm. During storms of this
type, the role of plasmaspheric fluxes dominates at middle
to low latitudes. Their effects are observable up to
subauroral latitudes given that the neutral composition
disturbance zone development is restricted to higher
latitudes, as happens when the geomagnetic activity is of
low or moderate intensity.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{bencze05,
author = {Bencze, P.},
title = {On the long-term change of ionospheric parameters},
journal = {jastp},
year = 2005,
volume = 67,
number = 14,
pages = {1298--1306},
month = {September},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1016/j.jastp.2005.06.020},
abstract = {Independent of the possible sources (solar activity,
geomagnetic activity, greenhouse effect, etc.) of a global
change in the upper atmosphere, it is the sign of a
long-term trend of temperature that might reveal the cause
of a global change. Long-term change of temperature in the
F region of the ionosphere has been studied and is assumed
to be expressed in terms of thickness of the bottornside F2
layer characterized by the difference between height of the
maximum electron density of the F2 layer hmF2 and altitude
of the lower boundary of the F region represented by
h'F. Using the difference of two ionospheric parameters has
the advantage that it reduces the effect of changes
resulting from alteration of equipment and scaling
personnel. In this study, in summer only night values of the
difference hmF2-h'F and in winter both day and night values
have been taken into account considering that h'F might
indicate the lower boundary of the F region in these
periods. The study of the behaviour of hmF2-h'F taking
separately the stations and determining yearly the mean
measure (trend) of the variation of hmF2-h'F with solar and
geomagnetic activities found that this difference increases
significantly with enhanced solar activity, but trends of
the solar activity effect exerted on this difference
themselves do not practically change with increasing sunspot
number. Further, hmF2-h'F decreases only insignificantly
with growing geomagnetic activity. Trends of the geomagnetic
activity effect related to hmF2-h'F change only
insignificantly with increasing Ap; however, trends of the
geomagnetic activity effect decreased with increasing
latitude. As a result of this investigation it has been
found that hmF2-h'F regarded as thickness of the bottornside
F2 layer shows an effect of the change of solar activity
during the last three solar cycles, indicating temperature
change in the upper atmosphere to be expected on the basis
of changing solar activity. Furthermore, though a long-term
variation of solar activity considering only years around
solar activity minima is relatively small, the difference
hmF2-h'F indicates a trend opposing the change of solar
activity; that is, it decreases slightly during the first
three 20, 21, 22 solar cycle minima (1964-1986), but
decreases more abruptly according to the change of solar
activity towards the minimum of solar cycle 23 (1986-1996),
thus also indicating variation of temperature in the F
region. However, this variation cannot be explained by the
change of solar and geomagnetic activities alone, but
assumes some other source (e.g. greenhouse gases) too.}
}
@techreport{besprozvannaya1982,
author = {Besprozvannaya, A.S. and Shchuka, T.I.},
title = {Atlas of Ionograms : A reference collection of ionograms
from high latitude stations},
institution = {The Arctic and Antarctic Research Institute},
year = {1982},
address = {USSR State Committee for Hydometeorology and Control of
Natural Environment, Leningrad},
note = {Compiled by the Ionogram Reduction Group},
ukssdc_d = {}
}
@article{bessarab2002,
author = {Bessarab, F.S. and Korenkov, Y.N. and Klimenko, V.V. and
Natsvalyan, N.S.},
title = {Modeling the thermospheric and ionospheric response to the
solar eclipse of August 11, 1999},
journal = {Annales Geophysicae},
year = {2002},
volume = {42},
number = {5},
pages = {644--651},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The results of model computations of thermospheric and
ionospheric effects of the solar eclipse of August 11, 1999,
are reported. The computations are performed in terms of a
self-consistent global model of the Earth's thermosphere,
ionosphere, and protonosphere. It is shown that during the
eclipse, the neutral gas temperature in the thermosphere
decreases by 90 K, absolute concentrations of $O$ and
$N_{2}$ components decrease by 20 and 40\%, respectively,
and the wind regime changes so that it allows the amplitude
of neutral gas velocity to change by 100 m/s. The results of
foF2 computations are compared to the experimental data
obtained at Chilton station ($51.3^{\circ}$N, $1^{\circ}$W)
during the eclipse of August 11, 1999. The decrease in foF2
reaches similar to 1 MHz. It is shown that some of the
thermospheric and ionospheric parameters do not rapidly
recover after the eclipse. In particular, $T_{n}$ and the
concentration of $N_{2}$ remained low above Chilton station
until the end of the day. The diurnal variation in foF2
increases at 1800 UT compared to undisturbed conditions.}
}
@article{bilge00,
author = {Bilge, A.H. and Tulunay, Y.K.},
title = {A novel on-line for single station prediction and
forecasting of the ionospheric critical frequency foF2 1
hour ahead},
journal = {Geophysical Research Letters},
pages = {1383--1386},
year = {2000},
month = {may},
volume = {27},
number = {9},
abstract = {The unpredictable variability of the ionospheric F region
greatly limits the efficiency of communications, radar and
navigation systems which employ high frequency (HF)
radiowaves. The objective of this work is to forecast the
ionospheric critical frequency values (foF2) one hour in
advance. For this a novel method has been developed for
1-hour ahead forecasting of the critical frequency of the F2
layer (foF2) based on applying feedback on predicted monthly
median values of foF2 for each hour. The basic model for the
prediction of the monthly medians consists of a parabolic
dependency on R12 superimposed by a trigonometric expansion
in terms of the harmonics of yearly variation, linearly
modulated by R12. The monthly medians for each hour are
predicted by applying the basic model over a sliding data
window.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{blanch2005,
author = {Blanch, E. and Altadill, D. and Boska, J. and Buresova, D.
and Hernandez-Pajares, M.},
title = {November 2003 event: Effects on the Earth's ionosphere
observed from ground-based ionosonde and GPS data},
journal = {Annales Geophysicae},
year = {2005},
volume = {23},
number = {9},
pages = {3027--3034},
ukssdc_d = {},
ukssdc_i = {},
url = {http://overview.sref.org/1432-0576/ag/2005-23-3027},
abstract = {Intense late-cycle solar activity during October and November
2003 produced two strong geomagnetic storms: 28 October-5
November 2003 (October) and 1923 November 2003 (November);
both reached intense geomagnetic activity levels, $K_{p} = 9$,
and $K_{p} = 8^{+}$, respectively. The October 2003 geomagnetic
storm was stronger, but the effects on the Earth's ionosphere
in the mid-latitude European sector were more important
during the November 2003 storm. The aim of this paper is to
discuss two significant effects observed on the ionosphere
over the mid-latitude European sector produced by the
November 2003 geomagnetic storm, using, data from ground
ionosonde at Chilton (51.5 degrees N; 359.4 degrees E),
Pruhonice (50.0 degrees N; 14.6 degrees E) and El Arenosillo
(37.1 degrees N; 353.3 degrees E), jointly with GPS data.
These effects are the presence of well developed anomalous
storm E, layers observed at latitudes as low as 37 degrees N
and the presence of two thin belts: one having enhanced
electron content and other, depressed electron content. Both
reside over the mid-latitude European evening sector.}
}
@article{blogoveshchensky03,
author = {Blogoveshchensky, D. V. and Maltseva, O. A. and Rodger,
A. S.},
title = {Ionosphere dynamics over Europe and western Asia during
magnetospheric substorms 1998-1999},
journal = {Annales Geophysicae},
pages = {1141-1151},
year = {2003},
volume = {21},
number = {5},
abstract = {The temporal and spatial behaviour of the ionospheric
parameters foF2 and h'F during isolated substorms are
examined using data from ionospheric stations distributed
across Europe and western Asia. The main purpose is finding
the forerunners of the substorm disturbances and a possible
prediction of these disturbances. During the period from
March 1998 to March 1999, 41 isolated substorms with
intensities I = 60 - 400 nT were identified and studied. The
study separated occasions when the local magnetometers were
affected by the eastward electrojet (positive substorms)
from those influenced by the westward electrojet (negative
substorms). The deviations of the ionospheric parameters
from their monthly medians (DfoF2 and Dh'F) have been used
to determine the variations through the substorm. Substorm
effects occurred simultaneously (< 1 h) across the entire
observatory network. For negative substorms, DfoF2-values
increase > 6 h before substorm onset, To, reaching a maximum
2-3 h before To. A second maximum occurs 1-2 h after the end
of the substorm. The Dh'F values 3-4 h before To have a
small minimum but then increase to a maximum at To. There is
a second maximum at the end of the expansion phase before
dh'F drops to a minimum 2-3 h after ending the expansion
phase. For positive substorms, the timing of the first
maximum of the dfoF2 and dh'F values depends on the substorm
length - if it is longer, the position is closer to To. The
effects on the ionosphere are significant: DfoF2 and Dh'F
reach 2-3 MHz (dfoF2 = 50-70\% from median value) and 50-70
km (D h'F = 20-30\% from median value), respectively. Regular
patterns of occurrence ahead of the first substorm signature
on the magnetometer offer an excellent possibility to
improve short-term forecasting of radio wave propagation
conditions.},
ukssdc_d = {}
}
@proceedings{bradley1976,
author = {Bradley, P.A.},
editor = {Bradley, P.A.},
title = {{A new computer-based method of HF sky-wave signal
prediction using vertical-incidence ionosonde measurements}},
booktitle = {AGARD Radio Systems and the Ionosphere 16 p (SEE N76-20302
11-32)},
year = 1976,
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=1976rsi..agarQ....B&db_key=INST},
adsnote = {Provided by the NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {A knowledge of ionospheric propagation modes and signal
strengths is important for the successful operation of HF
point-to-point communication circuits and over-the-horizon
radars. Predictions use representations of the state of the
ionosphere based either on long term trends in past
ionospheric data, or on near real time ionospheric soundings
at vertical incidence or over oblique paths. A new
prediction scheme is described which can be used with either
forecast values or direct measurements of the standard
ionospheric characteristics derived from vertical incidence
soundings. Its important features include an improved model
of the vertical distribution of electron concentration, a
homing procedure to determine the rays which travel between
specified terminals, an allowance for the focusing of rays
with low elevation angles, an expression for ionospheric
absorption based on the ionospheric characteristic foE and
the inclusion of the effects of polarization coupling loss
determined in terms of ray path and magnetic field
geometry.}
}
@unpublished{bradley1993,
author = {Bradley, P.A.},
title = {A study of the differences in foF2 and M(3000)F2 between
solar cycles},
year = {1993},
note = {Given at URSI GA 1993},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{bradley98:_instan_europ_hf,
author = {Bradley, P.A. and Juchnikowski, G. and Rothkaehl, H. and
Stanislawska, I.},
title = {Instantaneous maps of the European middle and high-latitude
ionosphere for HF propagation assessments},
journal = {Advances in Space Research},
pages = {861--864},
year = {1998},
month = oct,
volume = {22},
number = {6},
abstract = {Instantaneous mapping techniques applied to geographically
irregularly spaced foF2 measurements can lead sometimes to
non-physical gradients. A procedure is presented to avoid
such problems by the use of screen points within the area of
interest having values derived from single station models
(SSM's). Spatial smoothing uses the kriging method in terms
of the deviations between the measurements and corresponding
figures given by the adopted long-term mapping method of
COST 238 (PRIME). A new first-order trough model is
introduced as a correction to the mapped values on the
equatorial side of the auroral oval by night. Sample maps of
the European ionosphere generated by this technique are
compared with internationally recommended monthly median
prediction maps to demonstrate the lack of spatial structure
these latter give, with consequential errors when applied to
propagation assessments. The use of the new maps,
particularly for the higher latitudes, is advocated.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{bremer04:trends_ionosphere,
author = {Bremer, J.},
title = {Investigations of long-term trends in the ionosphere with
world-wide ionosonde observations},
journal = {Advances in Space Research},
year = {2004},
volume = 2,
pages = {253--258},
abstract = {Basing on model calculations by Roble and Dickinson (1989)
for an increasing content of atmospheric greenhouse gases in
the Earth's atmosphere Rishbeth (1990) predicted a lowering
of the ionospheric F2- and E-regions. Later Rishbeth and
Roble (1992) also predicted characteristic longterm changes
of the maximum electron density values of the ionospheric
E-, F1-, and F2-layers. Long-term observations at more than
100 ionosonde stations have been analyzed to test these
model predictions. In the E- and F1-layers the derived
experimental results agree reasonably with the model trends
(lowering of h0E and increase of foE and foF1, in the
E-layer the experimental values are however markedly
stronger than the model data). In the ionospheric F2-region
the variability of the trends derived at the different
individual stations for hmF2 as well as foF2 values is too
large to estimate reasonable global mean trends. The reason
of the large differences between the individual trends is
not quite clear. Strong dynamical effects may play an
important role in the F2-region. But also inhomogeneous data
series due to technical changes as well as changes in the
evaluation algorithms used during the long observation
periods may influence the trend analyses.},
url = {http://www.copernicus.org/URSI/ars/ARS_2_1/253.pdf},
ukssdc_d = {},
ukssdc_i = {}
}
@article{bremer98:_trend_e_f_europ,
author = {Bremer, J.},
title = {Trends in the ionospheric E and F regions over Europe},
journal = {Annales Geophysicae},
pages = {986--996},
year = {1998},
volume = {16},
number = {8},
abstract = {Continuous observations in the ionospheric E and F regions
have been regularly carried out since the fifties of this
century at many ionosonde stations. Using these data from 31
European stations long-term trends have been derived for
different parameters of the ionospheric E layer (h' E, foE),
F1 layer (foF1) and F2 layer (hmF2, foF2). The detected
trends in the E and F1 layers (lowering of the E region
height h'E; increase of the peak electron densities of the E
and F1 layers, foE and foF1) are in qualitative agreement
with model predictions of an increasing atmospheric
greenhouse effect. In the F2 region, however, the results
are more complex. Whereas in the European region west of
$30^{\circ}$E negative trends in hmF2 (peak height of the F2
layer) and in the peak electron density (foF2) have been
found, in the eastern part of Europe (east of $30^{\circ}$E)
positive trends dominate in both parameters. These marked
longitudinal differences cannot be explained by an
increasing greenhouse effect only, here probably dynamical
effects in the F2 layer seem to play an essential role.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{bremer04:_long_term,
author = {Bremer, J. and Alfonsi, L. and Bencze, P. and Lastovicka,
J. and Mikhailov, A.V. and Rogers, N.},
title = {Long-term trends in the ionosphere and upper atmosphere
parameters},
journal = {Annals of Geophysics},
pages = {1009--1029},
year = {2004},
volume = {47},
number = {2--3},
abstract = {The first part of the paper is directed to the investigation
of the practical importance of possible longterm trends in
the F2-layer for ionospheric prediction models. Using
observations of about 50 different ionosonde stations with
more than 30 years data series of foF2 and hmF2, trends have
been derived with the solar sunspot number R-12 as index of
the solar activity. The final result of this trend analysis
is that the differences between the trends derived from the
data of the individual stations are relatively large, the
calculated global mean values of the foF2 and hmF2 trends,
however, are relatively small. Therefore, these small global
trends can be neglected for practical purposes and must not
be considered in ionospheric prediction models. This
conclusion is in agreement with the results of other
investigations analyzing data of globally distributed
stations. As shown with the data of the ionosonde station
Tromso, however, at individual stations the ionospheric
trends may be markedly stronger and lead to essential
effects in ionospheric radio propagation. The second part of
the paper deals with the reasons for possible trends in the
Earth's atmo- and ionosphere as investigated by different
methods using characteristic parameters of the ionospheric
D-, E-, and F-regions. Mainly in the F2-region different
analyses have been carried out. The derived trends are
mainly discussed in connection with an increasing greenhouse
effect or by long-term changes in geomagnetic activity. In
the F I-layer the derived mean global trend in foF1 is in
good agreement with model predictions of an increasing
greenhouse effect. In the E-region the derived trends in foE
and h'E are compared with model results of an atmospheric
greenhouse effect, or explained by geomagnetic effects or
other anthropogenic disturbances. The trend results in the
D-region derived from ionospheric reflection height and
absorption measurements in the LF, MF and HF ranges can at
least partly be explained by an increasing atmospheric
greenhouse effect.},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{2006JATP...68.2075B,
author = {Bremer, J. and Cander, L.R. and Mielich, J. and Stamper, R.},
title = {{Derivation and test of ionospheric activity indices from
real-time ionosonde observations in the European region}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2006,
month = dec,
volume = 68,
pages = {2075-2090},
doi = {10.1016/j.jastp.2006.07.003},
adsurl = {http://adsabs.harvard.edu/abs/2006JATP...68.2075B},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {New ionospheric activity indices are derived from
automatically scaled online data from several European
ionosonde stations. These indices are used to distinguish
between normal ionospheric conditions expected from
prevailing solar activity and ionospheric disturbances
caused by specific solar and atmospheric events (flares,
coronal mass ejections, atmospheric waves, etc.). The most
reliable indices are derived from the maximum electron
density of the ionospheric F2-layer expressed by the maximum
critical frequency foF2. Similar indices derived from
ionospheric M(3000)F2 values show a markedly lower
variability indicating that the changes of the altitude of
the F2-layer maximum are proportionally smaller than those
estimated from the maximum electron density in the F
2-layer. By using the ionospheric activity indices for
several stations the ionospheric disturbance level over a
substantial part of Europe ($34^{\circ}$N $60^{\circ}$N;
$5^{\circ}$W $40^{\circ}$E) can now be displayed online.},
uk_other = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{bremer96:_influen_imf_f2,
author = {Bremer, J. and Lastovicka, W. and Tulunay, Y.K.},
title = {Influence of the IMF on the variability of the mid-latitude
F2-layer},
journal = {Annali di Geofisica},
pages = {721--727},
year = {1996},
volume = {EK-2},
number = {39},
abstract = {The structure of the Interplanetary Magnetic Field (IMF) is
responsible for an essential part of the variability of the
ionospheric plasma as demonstrated by investigations of the
influence of IMF sector boundary crossings as well as of
$B_{z}$-changes (defined from satellite observations) to
the maximal electron density of the F2-layer at different
stations in mid-latitudes. It could be shown that negative
$B_{z}$-values cause distinct negative ionospheric
effects. Maximal effects were detected at high geomagnetic
latitudes (ionospheric response decreases with decreasing
latitude), high solar/geomagnetic activity, equinoxes and
night-time conditions.},
ukssdc_d = {}
}
@article{brown1980a,
author = {Brown, G.M. and Evans, D.R.},
title = {The use of solar faculae in studies of the sunspot cycle},
journal = {Solar Physics},
pages = {233--243},
year = {1980},
volume = {66},
ukssdc_d = {},
uk_first = {}
}
@article{brown1980b,
author = {Brown, G.M. and Evans, D.R.},
title = {Latitude variations of photospheric activity areas with
particular reference to solar faculae},
journal = {Solar Physics},
pages = {141--149},
year = {1980},
month = {nov},
volume = {68},
abstract = {Detailed studies of the development of photospheric activity
centres for two solar cycles show that Spoerer's Law holds
in a very similar form to that applying to sunspots for the
faculae which inhabit the sunspot zones. Similar differences
between the two solar hemispheres can arise, and it seems to
be confirmed that the average latitude of faculae tends to
be a few degrees poleward of that of sunspots throughout a
given cycle. It is shown that the normal averaging process
involved in deriving Spoerer's Law obscures a detail which
is revealed in a breakdown into the variations within
successive narrow latitude strips. These show the existence
within a cycle of three separate maxima of activity
occurring at different epochs and with different preferred
latitudes. The main properties of these maxima are
discussed.},
ukssdc_d = {},
uk_first = {}
}
@article{buresova2000,
author = {Buresova, D. and Lastovicka, J.},
title = {Hysteresis of foF2 at European middle latitudes},
journal = {Annales Geophysicae},
year = {2000},
volume = {18},
number = {8},
pages = {987--991},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The hysteresis of foF2 is studied for several European
stations over the whole 24-hour diurnal interval for the
equinoctial months of the years just before and just after
the solar cycle minimum for solar cycles 20 and 21. Based on
previous results, the hysteresis is expected to develop best
just for the equinoctial months and near the solar cycle
minimum. The hysteresis is generally found to be negative,
i.e. higher foF2 for the rising branch compared to the
falling branch of solar cycle. However, this is not the case
in some individual months of some years. The noontime
hysteresis represents the hysteresis at other times of the
day qualitatively (as to sign) but not quantitatively. The
hysteresis appears to be relatively persistent from one
solar cycle to another solar cycle in spring but not in
autumn. A typical value for springtime hysteresis is about
0.5 MHz. The inclusion of hysteresis into longterm
ionospheric and radio wave propagation predictions remains
questionable.}
}
@article{buresova2001,
author = {Buresova, D. and Lastovicka, J.},
title = {Changes in the F1 region electron density during geomagnetic
storms at low solar activity},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2001},
volume = {63},
number = {5},
pages = {537--544},
ukssdc_d = {},
ukssdc_i = {},
abstract = {This paper attempts to demonstrate the changes in the F1
layer ionization during geomagnetic storm. To analyze the
behavior of F1 region, we have selected eight rather strong
geomagnetic storms that occurred in different seasons in
1994-1997. Their course was similar and there were at least
three quiet days before each event. The electron density
profiles for these events, derived from all the available
ionograms of the Pruhonice station (50 degrees N, 14.6
degrees E), were analyzed in order to investigate electron
density variability at heights of 160-190 km. Spring/autumn
asymmetry of the effects in F1 region is found. We observed
no significant effect of an ionospheric storm in electron
density in the F1 region during spring geomagnetic storms,
while there is a substantial effect in autumn at 180 and 190
km heights. We have compared our results with those obtained
from ionograms of some other European ionospheric
stations. In general, the F1 region appears to be much more
stable than the F2 layer during ionospheric
storms. Substantial intra-hour variability was found in NmF2
during geomagnetic storms in daytime, while it was very weak
on the storm maximum day in F1 layer.}
}
@article{buresova2002,
author = {Buresova, D. and Lastovicka, J. and Altadill, D. and Miro,
G.},
title = {Daytime electron density at the F1-region in Europe during
geomagnetic storms},
journal = {Annales Geophysicae},
year = {2002},
volume = {20},
number = {7},
pages = {1007--1021},
ukssdc_d = {},
ukssdc_i = {},
abstract = {This study attempts to demonstrate changes in the
ionospheric F1-region daytime ionization during geomagnetic
storms. The F1-region is explored using available data from
several European middle latitude and lower latitude
observatories and a set of geomagnetic storms encompassing a
range of seasons and solar activity levels. The results of
analysis suggest systematic seasonal and partly latitudinal
differences in the F1-region response to geomagnetic
storm. The pattern of the response of the F1-region at
higher middle latitudes, a decrease in electron density,
does not depend on the type of response of the F2-region and
on solar activity. A brief interpretation of these findings
is presented.}
}
@article{bust04,
author = {Bust, G. S. and Garner, T. W. and Gaussiran, T. L.},
title = {Ionospheric Data Assimilation Three-Dimensional (IDA3D): A
global, multisensor, electron density specification
algorithm},
url = {http://www.agu.org/pubs/crossref/2004.../2003JA010234.shtml},
journal = {Journal of Geophysical Research},
year = {2004},
month = {nov},
volume = {109},
number = {A11},
abstract = {With the advent of the Global Positioning System (GPS)
measurements (from both ground-based and satellite-based
receivers), the number of available ionospheric measurements
has dramatically increased. Total electron content (TEC)
measurements from GPS instruments augment observations from
more traditional ionospheric instruments like ionospheric
sounders and Langmuir probes. This volume of data creates
both an opportunity and a need for the observations to be
collected into coherent synoptic scale maps. This paper
describes the Ionospheric Data Assimilation
Three-Dimensional (IDA3D), an ionospheric objective analysis
algorithm. IDA3D uses a three-dimensional variational data
assimilation technique (3DVAR), similar to those used in
meteorology. IDA3D incorporates available data, the
associated data error covariances, a reasonable background
specification, and the expected background error covariance
into a coherent specification on a global grid. It is
capable of incorporating most electron density related
measurements including GPS-TEC measurements,
low-Earth-orbiting "beacon" TEC, and electron density
measurements from radars and satellites. At present, the
background specification is based upon empirical ionospheric
models, but IDA3D is capable of using any global ionospheric
specification as a background. In its basic form, IDA3D
produces a spatial analysis of the electron density
distribution at a specified time. A time series of these
specifications can be created using past specifications to
determine the background for the current analysis. IDA3D
specifications are able to reproduce dynamic features of
electron density, including the movement of the auroral
boundary and the strength of the trough region.},
ukssdc_d = {}
}
@article{butcher2005,
author = {Butcher, N.},
title = {Daily ionospheric forecasting service (DIFS) III},
journal = {Annales Geophysicae},
year = {2005},
volume = {23},
number = {12},
pages = {3591--3598},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
url = {http://overview.sref.org/1432-0576/ag/2005-23-3591},
abstract = {The daily variability of the ionosphere can greatly affect HF
or SATCOM communications. HF skywave operators plan frequency
schedules months in advance, however, they also require daily
knowledge of the ionospheric conditions in order to modify
assignments. SATCOM operators also require daily information
about the levels of scintillation, which are variations in
phase, amplitude, polarisation and angle of arrival that can
cause severe degradation of the received signal.
Using a number of ionosonde measurements and geomagnetic and
solar values, a Daily Ionospheric Forecasting Service (DIFS)
has been developed, which provides HF and SATCOM operators
with daily forecasts of predicted ionospheric conditions. The
system uses in-house algorithms and an externally developed
Global Ionospheric Scintillation Model (GISM) to generate HF
and SATCOM forecasts. HF forecasts consist of a past summary
and a forecast section, primarily displaying observed values
and predicted categories for the Maximum Usable Frequency
(MUF), as well as an Ionospheric Correction factor (ICF) that
can be fed into the ionospheric propagation prediction tool,
WinHF. SATCOM forecasts give predictions of global
scintillation levels, for the polar, mid and equatorial
latitude regions. Thorough analysis was carried out on DIFS
and the results conclude that the service gives good
accuracy, with user feedback also confirming this, as well.}
}
@article{cander01:_towar_cost,
author = {Cander, L.R.},
title = {Toward forecasting and mapping ionospheric space weather
under the COST actions},
journal = {Advances in Space Research},
pages = {957-964},
year = {2003},
volume = {31},
number = {4},
abstract = {Past COST projects 238 (PRIME) and 251 (IITS) encompassed a
variety of efforts to forecast and map the ionospheric
plasma response to disturbed geophysical conditions over the
European region. In a number of case studies they provided
useful guidelines for what could be achieved by different
theoretical, empirical and artificial neural network
techniques. New COST 271 action on 'Effects of the upper
atmosphere on terrestrial and Earth-space communications'
which began in the early months of the year 2000 is focusing
upon efforts to map the ionospheric space weather conditions
over Europe in near-real-time and to forecast these
conditions a few hours ahead. The purpose of the paper is to
present some of the findings from the previous COST 251
study and the plans for the new one (COST 271).},
ukssdc_d = {},
uk_first = {}
}
@inproceedings{cander01:_tec,
author = {Cander, L.R. and Ciraolo, L.},
title = {On ionospheric storms selection and TEC data to be used in
generating worst case scenarios},
booktitle = {Proceedings of the GNSS 2001},
year = {2001},
month = {May},
address = {Sevile},
ukssdc_d = {},
uk_first = {}
}
@article{cander04:_real-time_dynamic,
author = {Cander, L.R. and Hickford, J. and Tsagouri, I. and Belahaki,
A.},
title = {Real-time dynamic system for monitoring ionospheric
propagation conditions over Europe},
journal = {Electronics Letters},
pages = {224--226},
year = {2004},
volume = {40},
number = {4},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {Real-time measurements of the critical frequency of F-2
layer, foF(2), and the propagation factor for a 3000 kin
range, M(3000)F2 from four European Digisondes operating in
Athens, Rome, Chilton and Juliusruh and the Bz-component of
the interplanetary magnetic field, Bz-IMF, from the NASA
Advanced Composition Explorer (ACE) spacecraft mission are
combined for the development of a real-time dynamic system,
oriented to monitor the ionospheric propagation conditions
over Europe. The validity of the developed system in its
present operational form is investigated through the
analysis of two case study events. First results indicate a
temporal correlation between the Bz-IMF component
disturbances and the quantitative signature of ionospheric
disturbances at middle latitude, making the developed
facility a useful tool for modelling. and forecasting
ionospheric propagation conditions.}
}
@article{2005JATP...67.1118C,
author = {Cander, L.R. and Mihajlovic, S.J.},
title = {{Ionospheric spatial and temporal variations during the 29
31 October 2003 storm}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2005,
month = aug,
volume = 67,
pages = {1118-1128},
doi = {10.1016/j.jastp.2005.02.020},
adsurl = {http://adsabs.harvard.edu/abs/2005JATP...67.1118C},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {A prominent large-scale ionospheric disturbance was observed
in the European mid-latitude sector during the recent
extreme space weather event in October 2003. Measurements of
the horizontal component of the geomagnetic field H, the
critical frequency of the F2 layer foF2, and the vertical
total electron content (TEC) from the European network of
observational sites are used to describe the temporal and
spatial storm evolution process. It is found that the
ionospheric F region storm morphology was dominated by
negative disturbances over high mid-latitudes and positive
disturbance at low mid-latitudes during the initial phase
and by overall negative disturbances during the main
phase. Although a good agreement between the two independent
measurements was detected by comparing the storm-time
behaviour of foF2 and TEC during the main phase of the
storm, some irregularities have been recognised in TEC
variations at high mid-latitudes. The relative merit of
real-time observational solar-terrestrial data for accurate
specification of the geomagnetically disturbed ionospheric F
region during the extreme space weather conditions is
discussed. },
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{cander98:_forec,
author = {Cander, L.R. and Mihajlovic, S.J.},
title = {Forecasting ionospheric structure during the great
geomagnetic storms},
journal = {Journal of Geophysical Research},
pages = {391--398},
year = {1998},
volume = {103},
number = {A1},
abstract = {Characteristics of midlatitude ionospheric disturbances
during several great geomagnetic storms have been
investigated using data from the European geomagnetic
observatories and ionospheric stations with the aim of
developing the local forecasting models, as part of the
prediction and retrospective ionospheric modeling over
Europe project. Based on the analysis of the geomagnetic
storms of February 6, 1986, and March 13, 1989, a detailed
picture of the local H component of geomagnetic field and
the ionospheric critical frequency f0F2 variations is
presented. The results show that f0F2 was dramatically
changed above or below the monthly median level in a
relatively narrow band about $15^{\circ}$ of latitude and
$30^{\circ}$ longitude during the different phases of the
storms. These results support the view that day-to-day F
region ionospheric variability is essentially altered in
great storms. Consequences of those effects for short-term
modeling purposes are discussed.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{cander98:_ionos,
author = {Cander, L.R. and Milosavljevic, M.M. and Stankovic, S.S. and
Tomasevic, S.},
title = {Ionospheric forecasting technique by artificial neural
network},
journal = {Electronics Letters},
pages = {1573--1574},
year = {1998},
volume = {34},
number = {16},
abstract = {An artificial neural network method is applied to the
development of an ionospheric forecasting technique for one
hour ahead. Comparisons between the observed and predicted
values of the critical frequency of the F 2 layer, foF2, and
the total electron content (TEC) are presented to show the
appropriateness of the proposed technique.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{2005JATP...67.1053R,
author = {Cander, L.R. and Zolesi, B.},
title = {{Space weather and RF communications: Monitoring and
modelling}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2005,
month = aug,
volume = 67,
pages = {1053-1053},
doi = {10.1016/j.jastp.2005.05.001},
adsurl = {http://adsabs.harvard.edu/abs/2005JATP...67.1053R},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@techreport{chan01,
author = {Chan, A.H.Y. and Cannon, P.S.},
title = {A preliminary assessment of the spatial extrapolation of
foF2 predictions using nonlinear techniques},
institution = {DERA},
year = {2001},
number = {DERA/KIS/COM/TR010492},
ukssdc_d = {}
}
@inproceedings{chan01:_degrad,
author = {Chan, A.H.Y. and Cannon, P.S.},
title = {Degradation in neural network prediction models of foF2 with
time},
booktitle = {11th ICAP Conference Publication},
organization = {ICAP},
pages = {787--791},
year = {2001},
volume = {480},
ukssdc_d = {}
}
@article{chan2002,
author = {Chan, A.H.Y. and Cannon, P.S.},
title = {Nonlinear forecasts of foF2: variation of model predictive
accuracy over time},
journal = {Annales Geophysicae},
year = {2002},
volume = {20},
number = {7},
pages = {1031--1038},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {A nonlinear technique employing radial basis function neural
networks (RBF-NNs) has been applied to the short-term
forecasting of the ionospheric F2-layer critical frequency,
foF2. The accuracy of the model forecasts at a northern
mid-latitude location over long periods is assessed, and is
found to degrade with time. The results highlight the need
for the retraining and re-optimization of neural network
models on a regular basis to cope with changes in the
statistical properties of geophysical data sets. Periodic
retraining and re-optimization of the models resulted in a
reduction of the model predictive error by similar to 0.1 MHz
per six months. A detailed examination of error metrics is
also presented to illustrate the difficulties encountered in
evaluating the performance of various prediction/forecasting
techniques.}
}
@article{clilverd03,
author = {Clilverd, M. A. and Ulich, T. and Jarvis, M. J.},
title = {Residual solar cycle influence on trends in ionospheric
F2-layer peak height},
journal = {Journal of Geophysical Research},
year = {2003},
month = {dec},
volume = {108},
number = {A12},
abstract = {The longest data sets available for estimating thermospheric
temperature trends are those from ground-based ionosondes,
which often begin during the International Geophysical Year
of 1957, close to a solar activity maximum. It is important
to investigate inconsistencies in trend estimates from these
data sets so that trends can be clearly determined. Here we
use selected ionosonde stations to show that one of the most
significant factors affecting the trend estimates is the
removal of the solar cycle. The stations show trend behavior
that is close to the behavior of a theoretical model of
damped harmonic oscillation. The ringing features are
consistent with the presence of solar cycle residuals from
the analysis with an amplitude of 2.5 km. Some stations do
not show trend behavior that is close to either the average
behavior of the stations studied here or the theoretical
model of oscillation. Four European stations (Poitiers,
Lannion, Juliusruh, and Slough), three of which are closely
located in western Europe, were analyzed with the
expectation that their trend should be similar. Only
Poitiers and Juliusruh showed an evolution that was close to
the average behavior of other stations, while the other two
were significantly different. The primary cause of this
appears to be changes in the M(3000)F2 parameter and
demonstrates the importance of incorporating consistency
checks between neighboring ionosondes into global
thermospheric trend estimates.},
url = {http://dx.doi.org/10.1029/2003JA009838},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{clilverd05:_recon,
author = {Clilverd, M.A. and Clarke, E. and Ulich, T. and Linthe,
J. and Rishbeth, H.},
title = {Reconstructing the long-term aa index},
journal = {Journal of Geophysical Research},
year = 2005,
volume = 110,
number = {A7},
month = jul,
abstract = {The robustness of the aa geomagnetic index is of critical
importance to the debate about the previously reported
doubling of the solar coronal magnetic field in the last 100
years, inferred from an increasing trend in this index. To
test the trend in aa, we have reconstructed the aa index
using two long-running European stations (Sodankyla from
1914 and Niemegk from 1890) to provide data for the northern
component of the index that are independent of data from the
UK observatories used in the "official'' aa index. Both the
fully "reconstructed'' aa series, based on Sodankyla ( 67
degrees N, $L = 5.2 R_{E}$) and Niemegk ( 52 degrees N, $L =
2.3 R_{E}$) data in combination with the official aa
Southern Hemisphere data, confirm the increasing trend in
the index. The Niemegk-based index shows little solar cycle
variation in its deviation from the official index, probably
because of the midlatitude location of the station. The
high-latitude station, Sodankyla, is more affected by active
geomagnetic conditions during solar maximum because of the
proximity of the auroral oval to the station. Nevertheless,
its index also clearly confirms the increasing trend in the
aa index and hence supports the idea of a long-term increase
in solar coronal magnetic field strength. As an added test,
we reconstructed the aa index from a single site using data
from two long-running UK stations, Eskdalemuir and Lerwick,
applying a technique known as interhourly variation (IHV)
proposed by Svalgaard et al. (2004). The resulting series is
designed to be primarily sensitive to solar wind
conditions. Both the reconstructed aa(IHV) also showed an
increasing trend with time and high consistency with the
official aa index. Overall, we conclude that the robustness
of the trend in the aa index supports the idea of a
long-term increase in solar coronal magnetic field
strength.},
ukssdc_d = {},
uk_first = {}
}
@inproceedings{corbyn1992,
author = {Corbyn, Piers},
title = {Solar Activity and Long Range Weather Forecasting},
booktitle = {Fifth Conference on Changing Weather Patterns, Association
of British Insurers},
organization = {Association of British Insurers},
year = {1992},
month = feb,
address = {London},
volume = {5},
ukssdc_d = {},
uk_first = {}
}
@article{cowley91:_depen_x_y,
author = {Cowley, S. W. H. and Morelli, J.P. and Lockwood, M.},
title = {Dependence of convective flows and particle precipitation in
the high-latitude dayside ionosphere on the X and Y
components of the interplanetary magnetic field},
journal = {Journal of Geophysical Research},
year = 1991,
volume = 96,
number = {A4},
pages = {5557--5564},
ukssdc_d = {},
uk_first = {},
abstract = {The asymmetries in the convective flows, current systems,
and particle precipitation in the high-latitude dayside
ionosphere which are related to the equatorial plane
components of the interplanetary magnetic field (IMF) are
discussed in relation to the results of several recent
observational studies. It is argued that all of the effects
reported to date which are ascribed to the y component of
the IMF can be understood, at least qualitatively, in terms
of a simple theoretical picture in which the effects result
from the stresses exerted on the magnetosphere consequent on
the interconnection of terrestrial and interplanetary
fields. In particular, relaxation under the action of these
stresses allows, in effect, a partial penetration of the IMF
into the magnetospheric cavity, such that the sense of the
expected asymmetry effects on closed field lines can be
understood, to zeroth order, in terms of the "dipole plus
uniform field" model. In particular, in response to IMF By,
the dayside cusp should be displaced in longitude about noon
in the same sense as By in the northern hemisphere, and in
the opposite sense to By in the southern hemisphere, while
simultaneously the auroral oval as a whole should be shifted
in the dawn-dusk direction in the opposite sense with
respect to By. These expected displacements are found to be
consistent with recently published observations. Similar
considerations lead to the suggestion that the auroral oval
may also undergo displacements in the noon-midnight
direction which are associated with the x component of the
IMF. We show that a previously published study of the
position of the auroral oval contains strong initial
evidence for the existence of this effect. However, recent
results on variations in the latitude of the cusp are more
ambiguous. This topic therefore requires further study
before definitive conclusions can be drawn.}
}
@article{crooks03:_are,
author = {Crooks, S. and Allen, M. and Lockwood, M. and Gray, L. and
Stott, P. and Palmer, M.},
title = {Are models underestimating the effect of solar forcing on
climate?},
journal = {EGS - AGU - EUG Joint Assembly, Abstracts from the meeting
held in Nice, France, 6 - 11 April 2003, abstract \#14600},
year = 2003,
month = apr,
pages = {14600-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003EAEJA....14600C&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {It is important to correctly quantify the effect of solar
forcing of climate to gain a better understanding of the
factors that influence the overall climate system. Using an
"optimal fingerprinting" technique we find that current
climate models underestimate the observed climate response
to solar forcing over 11-year timescales, indicating that
the real climate system has a greater sensitivity to solar
forcing than current climate models responding to changes in
external TSI alone. Consideration of two sets of HadCM2
ensembles, each forced with a different reconstruction of
solar irradiance was employed in this analysis. In both
scenarios the simulated response is much weaker than the
observed, implying a need for a deeper understanding of
solar-climate interactions. This discrepancy is could be
attributable to a variation in the Earth's albedo over
periods in phase with characteristic solar timescales. The
proposed "Earthshine" mission seeks to investigate this
possibility using an instrument located at the L1 Lagrangian
point. Results from a preliminary signal-to-noise analysis
with a consideration of differing sections of the 11-year
solar cycle will be presented to show that a solar induced
variation in albedo could be detected by such an
instrument.}
}
@article{dabas2003,
author = {Dabas, R.S. and Kersley, L.},
title = {Radio tomographic imaging as an aid to modeling of
ionospheric electron density},
journal = {Radio Science},
year = {2003},
volume = {38},
number = {3},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
url = {http://dx.doi.org/10.1029/2001RS002514},
abstract = {Models of the ionosphere, used in applications for the
prediction or correction of propagation effects on practical
radio systems, are often inadequate in their representation
of the structure and development of large-scale features in
the electron density. Over northern Europe, characterization
of the main trough presents particular problems for such
empirical or parameterized models and hence for radio
propagation forecasting and ionospheric mapping. Results are
presented from a study aimed at investigating the possible
role of radio tomographic imaging in adapting models to
yield a better representation of the ionosphere over
Europe. It is shown that use of radio tomography gives
better agreement with actual ionosonde data than can be
obtained from any of the models used alone. It is suggested
that the technique may have a possible role in the mapping
of ionospheric conditions in near-real time for future
systems applications.}
}
@article{danilov2001:_f2region,
author = {Danilov, A.D.},
title = {F2-region response to geomagnetic disturbances},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
volume = {63},
number = {5},
year = {2001},
pages = {441--449},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The F2-region response to a geomagnetic storm usually called
a ionospheric storm is a rather complicated event. It
consists of the so-called positive an negative phases, which
have very complicated spatial and temporal behavior. During
the recent decade there was significant progress in
understanding this behavior. The principal features of the
positive and negative phase distribution and variations have
been explained on the basis of the principal concept: during
a geomagnetic disturbance there is an input of energy into
the polar ionosphere, which changes thermospheric
parameters, such as composition, temperature and
circulation. Composition changes directly influence the
electron concentration in the F2 region. The circulation
spreads the heated gas to lower latitudes. The conflict
between the storm-induced circulation and the regular one
determines the spatial distribution of the negative and
positive phases in various seasons. There are still problems
unsolved. The most acute ones are: the appearance of
positive phases before the beginning of a geomagnetic
disturbance, the occurrence of strong negative phases at the
equator, the role of vibrationally excited nitrogen in
forming the negative phase, and the relation of positive
phases to the dayside cusp. There are indications that the
f(o)F2 long-term trends revealed during the recent years may
be explained by long-term trends of the number of negative
ionospheric disturbances due to secular variations of the
geomagnetic activity.}
}
@article{danilov2003,
author = {Danilov, A.D.},
title = {Long-term trends of foF2 independent of geomagnetic
activity},
journal = {Annales Geophysicae},
year = {2003},
volume = {21},
number = {5},
pages = {1167--1176},
ukssdc_d = {},
ukssdc_i = {},
abstract = {A detailed analysis of the foF2 data at a series of
ionospheric stations is performed to reveal long-term trends
independent of the long-term changes in geomagnetic activity
during the recent decades (nongeomagnetic trends). The
method developed by the author and published earlier is
used. It is found that the results for 21 out of 23 stations
considered agree well and give a relative nongeomagnetic
trend of -0.0012 per year (or an absolute nongeomagnetic
trend of about -0.012 MHz per year) for the period between
1958 and the mid-nineties. The trends derived show no
dependence on geomagnetic latitude or local time, a fact
confirming their independence of geomagnetic activity. The
consideration of the earlier period (1948-1985) for a few
stations for which the corresponding data are available
provides significantly lower foF2 trends, the difference
between the later and earlier periods being a factor of
1.6. This is a strong argument in favor of an anthropogenic
nature of the trends derived.}
}
@article{danilov2001:_f2layer,
author = {Danilov, A.D. and Mikhailov, A.V.},
title = {F2-layer parameters long-term trends at the Argentine
Islands and Port Stanley stations},
journal = {Annales Geophysicae},
year = {2001},
volume = {19},
number = {3},
pages = {341--349},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The ionospheric sounding data at two southern hemisphere
stations, the Argentine Islands and Port Stanley, are
analyzed using a method previously developed by the
authors. Negative trends of the critical frequency foF2 are
found for both stations. The magnitudes of the trends are
close to those at the corresponding (dose geomagnetic
latitude) stations of the northern hemisphere, as considered
previously by the authors. The values of the F2 layer height
hmF2 absolute trends Delta hmF2 are considered. The effect
of Delta hmF2 dependence on hmF2 found by Jarvis et
al. (1998) is reproduced. A concept is considered that
long-term changes of the geomagnetic activity may be an
important (if not the only) cause of all the trends of foF2
and hmF2 derived by several groups of authors. The
dependence of both parameters on the geomagnetic index Ap
corresponds to a smooth scheme of the ionospheric storm
physics and morphology; thus, a principal cause of the foF2
and hmF2 geomagnetic trends is most probably a trend found
in several publications in the number and intensity of
ionospheric storms.}
}
@article{danilov2001:_long,
author = {Danilov, A.D. and Mikhailov, A.V.},
title = {Long-term trends in the F2-layer parameters at Argentine
Island and Port Stanley stations},
journal = {Annales Geophysicae},
year = {2001},
volume = {41},
number = {4},
pages = {488--496},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The data of vertical ionospheric sounding at Argentine
Island and Port Stanley stations in the Southern Hemisphere
are analyzed using the method of long-term trends developed
by us earlier. The negative trends in the critical frequency
f(0)F2 have been found for both stations. The trend
magnitudes are similar to such magnitudes at stations
located at close geomagnetic latitudes in the Northern
Hemisphere and considered by us earlier. The values of the
absolute trends in the F2 layer height (hmF2, Delta hmF2)
are considered. The effect of the Delta hmF2 dependence on
hmF2 determined by Jarvis et al. [1998] is reproduced. A
conclusion is drawn that all trends in f(0)F2 and hmF2
derived by different groups of authors have a geomagnetic
origin and are a manifestation of the long-term changes in
the geomagnetic activity. It has been shown that the
dependence of both parameters on the geomagnetic index Ap
corresponds to a smoothed scheme of the physics and
morphology of the ionospheric storms. The trends in both
ionospheric parameters (f(0)F2 and hmF2) apparently reflect
the long-term trends in the number and intensity of the
ionospheric storms found in several publications.}
}
@article{davis1997,
author = {Davis, C. J. and Wild, M. N. and Lockwood, M. and Tulunay, Y. K.},
affiliation = {Rutherford Appletpn Laboratory Chilton Didcot OX11 OQX
United Kingdom},
title = {Ionospheric and geomagnetic responses to changes in {IMF}
${B}_{z}$: a superposed epoch study},
journal = {Annales Geophysicae},
publisher = {Springer Berlin / Heidelberg},
issn = {0992-7689},
keyword = {Earth and Environmental Science},
pages = {217-230},
volume = 15,
issue = 2,
url = {http://dx.doi.org/10.1007/s00585-997-0217-9},
doi = {10.1007/s00585-997-0217-9},
abstract = {Superposed epoch studies have been carried out in order to
determine the ionospheric response at mid-latitudes to
southward turnings of the interplanetary magnetic field
(IMF). This is compared with the geomagnetic response, as
seen in the indices ${K}_{p}$, ${AE}$ and $Dst$. The solar
wind, IMF and geomagnetic data used were hourly averages
from the years 1967--1989 and thus cover a full 22-year
cycle in the solar magnetic field. These data were divided
into subsets, determined by the magnitudes of the southward
turnings and the concomitant increase in solar wind
pressure. The superposed epoch studies were carried out
using the time of the southward turning as time zero. The
response of the mid-latitude ionosphere is studied by
looking at the F-layer critical frequencies, $f_{o}F2$, from
hourly soundings by the Slough ionosonde and their deviation
from the monthly median values, ${\delta}f_{o}F2$. For the
southward turnings with a change in $B_{z}$ of
${\delta}B_{z}>11.5$ nT accompanied by a solar wind dynamic
pressure $P$ exceeding 5 nPa, the F region critical
frequency, $f_{o}F2$, shows a marked decrease, reaching a
minimum value about 20 h after the southward turning. This
recovers to pre-event values over the subsequent 24 h, on
average. The $Dst$ index shows the classic storm-time
decrease to about -60 nT. Four days later, the index has
still to fully recover and is at about -25 nT. Both the
$K_{p}$ and $AE$ indices show rises before the southward
turnings, when the IMF is strongly northward but the solar
wind dynamic pressure is enhanced. The average $AE$ index
does register a clear isolated pulse (averaging 650 nT for 2
h, compared with a background peak level of near 450 nT at
these times) showing enhanced energy deposition at high
latitudes in substorms but, like $K_{p}$, remains somewhat
enhanced for several days, even after the average IMF has
returned to zero after 1 day. This $AE$ background decays
away over several days as the $Dst$ index recovers,
indicating that there is some contamination of the currents
observed at the $AE$ stations by the continuing enhanced
equatorial ring current. For data averaged over all seasons,
the critical frequencies are depressed at Slough by 1.3 MHz,
which is close to the lower decile of the overall
distribution of ${\delta}f_{o}F2$ values. Taking 30-day
periods around summer and winter solstice, the largest
depression is 1.6 and 1.2 MHz, respectively. This seasonal
dependence is confirmed by a similar study for a Southern
Hemisphere station, Argentine Island, giving peak
depressions of 1.8 MHz and 0.5 MHz for summer and
winter. For the subset of turnings where
${\delta}B_{z}>11.5$ nT and $P<= 5$ nPa, the response of the
geomagnetic indices is similar but smaller, while the change
in ${\delta}f_{o}F2$ has all but disappeared. This confirms
that the energy deposited at high latitudes, which leads to
the geomagnetic and ionospheric disturbances following a
southward turning of the IMF, increases with the energy
density (dynamic pressure) of the solar wind flow. The
magnitude of all responses are shown to depend on
${\delta}B_{z}$. At Slough, the peak depression always
occurs when Slough rotates into the noon sector. The largest
ionospheric response is for southward turnings seen between
15--21 UT.},
uk_first = {},
ukssdc_w = {},
ukssdc_d = {},
ukssdc_i = {},
pdf = {http://www.ann-geophys.net/15/217/1997/angeo-15-217-1997.pdf},
year = 1997
}
@article{davis2001,
author = {Davis, C.J. and Clarke, E.M. and Bamford, R.A. and Lockwood,
M. and Bell, S.A.},
title = {Long term changes in EUV and X-ray emissions from the solar
corona and chromosphere as measured by the response of the
Earth's ionosphere during total solar eclipses from 1932 to
1999},
journal = {Annales Geophysicae},
pages = {263--273},
year = {2001},
volume = {19},
pdf = {http://www.copernicus.org/EGU/annales/19/ag19/263.pdf},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {Measurements of the ionospheric E region during total solar
eclipses in the period 1932-1999 have been used to
investigate the fraction of Extreme Ultra Violet and soft
X-ray radiation, phi, that is emitted from the limb corona
and chromosphere. The relative apparent sizes of the Moon
and the Sun are different for each eclipse, and techniques
are presented which correct the measurements and, therefore,
allow direct comparisons between different eclipses. The
results show that the fraction of ionising radiation emitted
by the limb corona has a clear solar cycle variation and
that the underlying trend shows this fraction has been
increasing since 1932. Data from the SOHO spacecraft are
used to study the effects of short-term variability and it
is shown that the observed long-term rise in phi has a
negligible probability of being a chance occurrence.}
}
@article{davis2005,
author = {Davis, C.J. and Johnson, C.G.},
title = {Lightning-induced intensification of the ionospheric sporadic E layer},
journal = {Nature},
pages = {799--801},
year = {2005},
volume = {435},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {A connection between thunderstorms and the ionosphere has
been hypothesized since the mid-1920s(1). Several mechanisms
have been proposed to explain this connection(2-7), and
evidence from modelling(8) as well as various types of
measurements(9-14) demonstrate that lightning can interact
with the lower ionosphere. It has been proposed, on the
basis of a few observed events(15), that the ionospheric
'sporadic E' layer - transient, localized patches of
relatively high electron density in the mid-ionosphere E
layer, which significantly affect radio-wave propagation -
can be modulated by thunderstorms, but a more formal
statistical analysis is still needed. Here we identify a
statistically significant intensification and descent in
altitude of the mid-latitude sporadic E layer directly above
thunderstorms. Because no ionospheric response to
low-pressure systems without lightning is detected, we
conclude that this localized intensification of the sporadic
E layer can be attributed to lightning. We suggest that the
co-location of lightning and ionospheric enhancement can be
explained by either vertically propagating gravity waves
that transfer energy from the site of lightning into the
ionosphere, or vertical electrical discharge, or by a
combination of these two mechanisms.}
}
@article{davis2000,
author = {Davis, C.J. and Lockwood, M. and Bell, S.A. and Smith,
J.A. and Clarke, E.M.},
title = {Ionospheric measurements of relative coronal brightness
during the total solar eclipses of 11 August, 1999 and 9
July, 1945},
journal = {Annales Geophysicae},
pages = {182--190},
year = {2000},
volume = {18},
number = {2},
abstract = {Swept-frequency (1-10 MHz) ionosonde measurements were made
at Helston, Cornwall ($50^{\circ}06'$N, $5^{\circ}18'$W)
during the total solar eclipse on August 11, 1999. Soundings
were made every three minutes. We present a method for
estimating the percentage of the ionising solar radiation
which remains unobscured at any time during the eclipse by
comparing the variation of the ionospheric E-layer with the
behaviour of the layer during a control day. Application to
the ionosonde date for 11 August, 1999, shows that the flux
of solar ionising radiation fell to a minimum of $25\pm2\%$
of the value before and after the eclipse. For comparison,
the same technique was also applied to measurements made
during the total solar eclipse of 9 July, 1945, at
S\"{o}rmj\"{o}le ($63^{\circ}68'$N, $20^{\circ}20'$E) and
yielded a corresponding minimum of $16\pm2\%$. Therefore the
method can detect variations in the fraction of solar
emissions that originate from the unobscured corona and
chromosphere. We discuss the differences between these two
eclipses in terms of the nature of the eclipse, short-term
fluctuations, the sunspot cycle and the recently-discovered
long-term change in the coronal magnetic field.},
url = {http://www.ann-geophys.net/18/182/2000/angeo-18-182-2000.html},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
pdf = {http://www.ann-geophys.net/18/182/2000/angeo-18-182-2000.pdf}
}
@article{defran01,
author = {De Franceschi, G. and Gulyaeva, T.L. and Perrone, L. and
Zolesi, B.},
title = {A long-term statistical analysis of the ionospheric
irregularities},
journal = {J. of Inverse Problems},
pages = {67-78},
year = {2001},
month = {jan},
volume = {18},
abstract = {Long timeseries of the critical frequency of the F2 layer,
foF2, from several mid- and high-latitude stations, are used
for investigating the average behaviour of the disturbed
ionospheric conditions identified by descriptive letters
replacing or accompanying the ionogram scaled value. By
analysing the distribution of the descriptive letters A
(sporadic Es layer presence), B (absorption near fmin ),
spread F appearance, G (screen by F1 layer) and R
(absorption near foF2), the mean percentage occurrence of
the ionospheric irregularities are calculated for four
specified levels of magnetic activity according to a new
magnetic activity catalogue (MAC) recently introduced for
studying the dependence of the ionosphere on magnetic
perturbations. After removing solar cycle effects from the
statistical results obtained, it is found that the total
bottomside irregularities increase with geomagnetic
latitudes and represent an indicator of the ionospheric
response to the magnetic activity with a time delay of the
order of about 15 h according to the MAC.},
ukssdc_d = {}
}
@article{deminov01:_long_f2,
author = {Deminov, M.G. and Garbatsevich, A.V. and Deminov, R.G.},
title = {Long-term variations in the critical frequency of the
midlatitude F2 layer at noon},
journal = {Geomagnetism and Aeronomy},
pages = {102--108},
year = {2001},
volume = {40},
number = {1},
ukssdc_d = {}
}
@article{deminov03:_long_E,
author = {Deminov, M.G. and Kolesnik, A.G. and Leshchenko, L.N. and
Sitnov, Y.S. and Tsybikov, B.B.},
title = {Climatic variations in the ionospheric E-layer noon critical
frequencies at midlatitudes},
journal = {Annales Geophysicae},
pages = {356--362},
year = {2003},
volume = {43},
number = {3},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The noon median values of the E-layer critical frequency
(foE) measured at Slough/Chilton (1931-1997), Moscow
(1946-1997), and Tomsk (1938-1997) stations have been
analyzed. New regularities in the foE climatic (long-term)
variations, the regression dependences of these variations
on the Wolf numbers averaged over 11 years (R-11, a global
factor), and the surface air temperature near a particular
station minus the temperature at the ocean-continent
boundary (DeltaT(11), a regional factor) have been
determined. The global factor predominates for
Slough/Chilton station located in the vicinity of the
ocean-continent boundary. The additional regression
dependence of foE on DeltaT(11) is substantial and
significant for the continental stations (the continental
effect). For Tomsk, this effect is even a predominant cause
of climatic variations in foE.}
}
@article{denton09:_modif_f2,
author = {Denton, M. H. and Ulich, T. and Turunen, E.},
title = {Modification of midlatitude ionospheric parameters in the F2
layer by persistent high‐speed solar wind streams},
journal = {Space Weather},
year = 2009,
doi = {doi:10.1029/2008SW000443},
volume = 7,
number = {S04006},
abstract = {High-speed solar wind streams (HSSs) are periods of
persistently high solar wind, which emanate from coronal
holes and may recur with a frequency related to the solar
rotation period of 27 days. On arrival at the Earth's
magnetopause, such streams cause a series of events which
ultimately lead to changes in the ionospheric F layer. We
present a superposed epoch analysis of parameters in the
midlatitude F2 layer for a collection of 124 high-speed
solar wind streams which occurred between 1993 and
2006. Clear changes in the critical frequency (foF2),
density (NmF2), and height (hmF2) are found to occur after
the onset of magnetospheric convection associated with HSS
arrival at the Earth's magnetosphere. A fall in foF2 occurs
immediately following convection onset accompanied by a
sudden decrease in NmF2 and an increase in hmF2. During the
events under study, the height of the F2 layer is found to
increase by $\sim20$ km at convection onset. A period of more
than 4 days is required for the ionosphere to return to
preevent levels. This behavior is explained as the
occurrence of ionospheric F region storms following HSS
arrival. The results raise the possibility of improved
predictions for ionospheric parameters on the basis of
upstream solar wind conditions and prior identification of
stream interfaces.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {},
pdf = {http://eprints.lancs.ac.uk/28033/1/art_967.pdf},
url = {http://www.agu.org/journals/ABS/2009/2008SW000443.shtml}
}
@article{denton02:_effec_chang_solar_euv_flux,
author = {Denton, M.~H. and Pryse, S.~E. and Sims, R.~W. and
Balthazor, R.~L.},
title = {{The Effects of Changing Solar Euv Flux Upon The Location
and Structure of The Dayside High-latitude Trough In Winter:
Modelling Results and Experimental Validation}},
journal = {EGS XXVII General Assembly, Nice, 21-26 April 2002, abstract
\#1388},
year = 2002,
volume = 27,
pages = {1388-+},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002EGSGA..27.1388D&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {The effects of changing solar EUV flux upon the location and
structure of the dayside high-latitude trough are
investigated, using a combination of modelling studies and
experimental ionospheric tomography. An increase in the EUV
radiation incident upon the atmosphere causes thermal
expansion, and an increase in ionisation. This drives
ionospheric features such as troughs to a greater
height. However, such behaviour is further complicated by
increased solar activity changing the chemical composition
of the atmosphere, and the fact that many of the chemical
reactions of importance to the ionosphere are temperature
dependent. Since a complete understanding of the variation
of ionospheric temperature with solar activity remains
elusive, the effects of the above processes upon the dayside
high-latitude trough cannot be predicted. In the present
paper results from theoretical modelling using the Coupled
Thermosphere-Ionosphere-Plasmasphere model are compared with
tomographic observations of the ionosphere. Calculations
have been performed for low, medium and high solar activity
and compared with tomographic reconstructions of ionospheric
electron density, taken under broadly similar conditions,
when geomagnetic activity was low. The results show that the
trough is driven polewards in latitude, and that the density
gradient equatorwards of the trough increases significantly,
as solar activity increases. However, the basic structure
and form of the trough are little changed. There is broad
agreement between the CTIP modelling calculations and the
experimental tomography observations.}
}
@article{depuev01:_using,
author = {Depuev, V.Kh. and Rotanova, N.M. and Depuev, A.Kh.},
title = {Using the wavelet transform to investigate the
spatial-temporal characteristics of the ionosphere},
journal = {Geomagnetism and Aeronomy},
pages = {88--93},
year = {2001},
volume = {41},
number = {1},
ukssdc_d = {}
}
@inproceedings{dick99:_short_europ,
author = {Dick, M.I. and Levy, M.F. and Cander, L.R. and Kutiev,
I. and Muhtarov, P.},
title = {Short-term ionospheric forecasting over Europe},
booktitle = {IEE National Conference on Antennas and Propagation},
pages = {105--107},
year = {1999},
ukssdc_d = {},
uk_first = {}
}
@article{2007JATP...69..621E,
author = {Echer, E.},
title = {{On the quasi-biennial oscillation (QBO) signal in the foF2
ionospheric parameter}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2007,
month = apr,
volume = 69,
pages = {621-627},
doi = {10.1016/j.jastp.2006.11.001},
adsurl = {http://adsabs.harvard.edu/abs/2007JATP...69..621E},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
ukssdc_i = {}
}
@article{2006JATP...68.1871E,
author = {Elias, A.G. and Ortiz de Adler, N.},
title = {{Earth magnetic field and geomagnetic activity effects on
long-term trends in the F2 layer at mid-high latitudes}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2006,
month = dec,
volume = 68,
pages = {1871-1878},
doi = {10.1016/j.jastp.2006.02.008},
adsurl = {http://adsabs.harvard.edu/abs/2006JATP...68.1871E},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
ukssdc_i = {}
}
@article{farges2001,
author = {Farges, T. and Jodogne, J.C. and Bamford, R. and Le Roux,
Y. and Gauthier, F. and Vila, P.M. and Altadill, D. and
Sole, J.G. and Miro, G.},
title = {Disturbances of the western European ionosphere during the
total solar eclipse of 11 August 1999 measured by a wide
ionosonde and radar network},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2001},
volume = {63},
number = {9},
pages = {915--924},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
abstract = {The 11 August 1999 Solar eclipse totality path ran across
western Europe at near-constant latitudes of about 49
degreesN. It occurred at mid-time of a sequence of three
days with steady solar wind and quiet magnetospheric
conditions. Its response was observed by a score of
ionospheric facilities, which will provide high-resolution
probing of the various disturbances. First results allow us
to compare the time fluctuations at various distances from
totality on the eclipse and adjacent days, inside a 5
degrees West to 5 degrees East longitude area. In this
preliminary work the foF1 and foF2 time changes are
presented in contour maps on a 50 km size grid. They show
the expected longitude transit of eclipse perturbation. We
venture brief comments on the eclipse-own signatures as
separate from the various wave oscillations detected prior
to eclipse time by 12.4 MHz panoramic azimuth scans of the
Losquet radar near Lannion (Brittanny).}
}
@article{farrugia1989,
author = {Farrugia, C.J. and Freeman, M.P. and Cowley, S.W.H. and
Southwood, D.J. and Lockwood, M. and Etemadi, A.},
title = {Pressure-driven magnetopause motions and attendant response
on the ground},
journal = {Planetary and Space Science},
pages = {589--607},
year = {1989},
volume = {37},
number = {5},
abstract = {The terrestrial magnetopause suffered considerable sudden
changes in its location on 9-10 September 1978. These
magnetopause motions were accompanied by disturbances of the
geomagnetic field on the ground. We present a study of the
magnetopause motions and the ground magnetic signatures
using, for the latter, 10 s averaged data from 14 high
latitude ground magnetometer stations. Observations in the
solar wind (from IMP 8) are employed and the motions of the
magnetopause are monitored directly by the spacecraft ISEE 1
and 2. With these coordinated observations we are able to
show that it is the sudden changes in the solar wind dynamic
pressure that are responsible for the disturbances seen on
the ground. At some ground stations we see evidence of a
``ringing'' of the magnetospheric cavity, while at others
only the initial impulse is evident. We note that at some
stations field perturbations closely match the hypothesized
ground signatures of flux transfer events. In accordance
with more recent work in the area (e.g. Potemra et al.,
1989, J. geophys. Res., in press), we argue that causes
other than impulsive reeonnection may produce the twin
ionospheric flow vortex originally proposed as a flux
transfer even signature.},
ukssdc_d = {},
uk_other = {}
}
@article{2007AnGeo..25..495F,
author = {Finch, I. and Lockwood, M.},
title = {{Solar wind-magnetosphere coupling functions on timescales
of 1 day to 1 year}},
journal = {Annales Geophysicae},
year = 2007,
month = mar,
volume = 25,
pages = {495-506},
adsurl = {http://adsabs.harvard.edu/abs/2007AnGeo..25..495F},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {There are no direct observational methods for determining
the total rate at which energy is extracted from the solar
wind by the magnetosphere. In the absence of such a direct
measurement, alternative means of estimating the energy
available to drive the magnetospheric system have been
developed using different ionospheric and magnetospheric
indices as proxies for energy consumption and dissipation
and thus the input. The so-called coupling functions are
constructed from the parameters of the interplanetary
medium, as either theoretical or empirical estimates of
energy transfer, and the effectiveness of these coupling
functions has been evaluated in terms of their correlation
with the chosen index. A number of coupling functions have
been studied in the past with various criteria governing
event selection and timescale. The present paper contains an
exhaustive survey of the correlation between geomagnetic
activity and the near-Earth solar wind and two of the
planetary indices at a wide variety of timescales. Various
combinations of interplanetary parameters are evaluated with
careful allowance for the effects of data gaps in the
interplanetary data. We show that the theoretical coupling,
$P_{\alpha}$, function first proposed by Vasyliunas et
al. is superior at all timescales from 1-day to 1-year.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{finch03:_long_term_chang_annual_diurn,
author = {Finch, I. and Lockwood, M.},
title = {Long-Term Changes in the Annual and Diurnal Variations of
Geomagnetic Indices},
journal = {EGS - AGU - EUG Joint Assembly, Abstracts from the meeting
held in Nice, France, 6 - 11 April 2003, abstract \#11601},
year = 2003,
month = apr,
pages = {11601-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003EAEJA....11601F&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {Recent research by on the am geomagnetic data series,
recording of which began in 1958, suggests that the
Russell-McPherron (RM) effect is not responsible for the
majority of annual and diurnal variations detected in
geophysical indices, rather a so-called "equinoctial effect"
is dominant. We demonstrate a simple conversion of the aa
index (which, with only two antipodal stations, has
difficulty resolving diurnal variations) into a proxy am
index, allowing us to extend the analysis back to 1868. The
case for the equinoctial effect becomes less compelling as
we examine the earlier data. Additionally examination of in
situ solar wind measurements shows that the RM effect is
clearly visible in geophysical indices for slow solar wind
but not for fast. Sargent's recurrence index is used to
extend these results to the extended am index.}
}
@article{forbes2000,
author = {Forbes, J.M. and Palo, S.E. and Zhang, X.L.},
title = {Variability of the ionosphere},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2000},
volume = {62},
number = {8},
pages = {685--693},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Hourly foF2 data from over 100 ionosonde stations during
1967-89 are examined to quantify F-region ionospheric
variability, and to assess to what degree the observed
variability may be attributed to various sources, i.e.,
solar ionizing Aux, meteorological influences, and changing
solar wind conditions. Our findings are as follows. Under
quiet geomagnetic conditions ($K_{p} < 1$), the 1-sigma
(sigma is the standard deviation) variability of N-max about
the mean is approx. $\pm25-35\%$ at 'high frequencies'
(periods of a few hours to 1-2 days) and
approx. $\pm15-20\%$ at 'low frequencies' (periods
approx. 2-30 days), at all latitudes. These values provide a
reasonable average estimate of ionospheric variability
mainly due to "meteorological influences" at these
frequencies. Changes in N-max due to variations in solar
photon flux, are, on the average, small in comparison at
these frequencies. Under quiet conditions for high-frequency
oscillations, N-max is most variable at anomaly peak
latitudes. This may reflect the sensitivity of anomaly peak
densities to day-to-day variations in F-region winds and
electric fields driven by the E-region wind
dynamo. Ionospheric variability increases with magnetic
activity at all latitudes and for both low and high
frequency ranges, and the slopes of all curves increase with
latitude. Thus, the responsiveness of the ionosphere to
increased magnetic activity increases as one progresses from
lower to higher latitudes. For the 25\% most disturbed
conditions ($K_{p} > 4$), the average 1-sigma variability of
N-max about the mean ranges from approx. $\pm35\%$ (equator)
to approx. $\pm45\%$ (anomaly peak) to approx. $\pm55\%$
(high-latitudes) for high frequencies, and from
approx. $\pm25\%$ (equator) to approx. $\pm45\%$
(high-latitudes) at low frequencies. Some estimates are also
provided on N-max variability connected with annual,
semiannual and Ii-year solar cycle variations.}
}
@article{foster01:_long,
author = {Foster, S. and Lockwood, M.},
title = {Long-term changes in the solar photosphere associated with
changes in the coronal source flux},
journal = {Geophysical Research Letters},
pages = {1443--1446},
year = {2001},
volume = {28},
number = {8},
abstract = {Using sunspot observations from Greenwich and Mount Wilson,
we show that the latitudinal spread of sunspot groups has
increased since 1874, in a manner that closely mirrors the
long-term (~100 year) changes in the coronal source flux,
$F_{S}$, as inferred from geomagnetic activity. This
latitude spread is shown to be well correlated with the flux
emergence rate required by the model of the coronal source
flux variation by Solanki et al. [2000]. The time constant
for the decay of this open flux is found to be $3.6\pm0.8$
years. Using this value, and quantifying the photospheric
flux emergence rate using the latitudinal spread of sunspot
groups, the model reproduces the observed coronal source
flux variation. The ratio of the 100-year drift to the solar
cycle amplitude for the flux emergence rate is found to be
half of the same ratio for $F_{S}$.},
ukssdc_d = {},
uk_first = {}
}
@article{foster03:_long,
author = {Foster, S. and Lockwood, M.},
title = {Long-term evolution of the open solar magnetic flux
associated with bipolar magnetic region tilts and latitudes},
journal = {EGS - AGU - EUG Joint Assembly, Abstracts from the meeting
held in Nice, France, 6 - 11 April 2003, abstract \#6298},
year = 2003,
month = apr,
pages = {6298-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003EAEJA.....6298F&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {When modelling the evolution of emerged magnetic flux
threading the solar surface, and the open solar flux that
results, two factors are critical for each newly-emerged
bipolar magnetic region (BMR), namely its latitude and the
tilt angle of the line connecting the centres of the two
opposite polarity regions. The variation of the former
throughout the solar cycle is given by the well-known
butterfly diagram, however the behaviour of the latter is
not so clearly defined. Using magnetogram observations of
BMRs, a systematic variation of average tilt angle with
heliographic latitude, and thus with the solar cycle phase,
has been reported and used in several modelling
studies. However, using observations of sunspot pairs no
such variation is apparent. We here investigate various
subsets of the tilt angle data from sunspots in an attempt
to reconcile and understand these apparently contradictory
results.}
}
@article{foster02:_long_solar_irrad_facul_variab,
author = {Foster, S.S. and Lockwood, M.},
title = {Long-term Solar Irradiance and Facular Variability
Associated With Changes In The Coronal Source Flux},
journal = {EGS XXVII General Assembly, Nice, 21-26 April 2002, abstract
\#4517},
year = 2002,
volume = 27,
pages = {4517-+},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002EGSGA..27.4517F&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {Monthly values of coronal source flux have been created
dating back until 1868 using the geomagnetic aa index
(Lockwood et al, 1999). These values have been found to
correlate well with the composite solar irradiance variation
compiled from measurements by Virgo, Acrim I and II, HF and
ERBS instrumentation (Frohlich and Lean, 1998). Using the
monthly values of $F_{S}$ as a proxy for solar irradiance,
we were able to reconstruct solar irradiance back to
1868. We have also created a model of PSI (photometric
sunspot index) dating back until 1874, using sunspot area as
a proxy. Combing both of these models we have been able to
reconstruct the facular bright- ening (including quiet sun)
variations since 1874. We also continue our investigation
using annual values of coronal source flux and PSI (from
sunspot number) to look at facular behaviour at all times
since the end of the Maunder minimum.}
}
@inproceedings{foster03:_bmrs_long_term_evolut_open_solar_flux,
author = {Foster, S.S. and Lockwood, M.},
title = {Bmrs and the Long-Term Evolution of the Open Solar Flux},
booktitle = {IAU Symposium},
year = 2003,
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003IAUS..219E..83F&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {Using Greenwich sunspot records and a model of open flux
evolution for individual bipolar magnetic regions (BMRs) we
investigate reconstructing the variations of the total open
solar flux and it's rate of emergence for the interval 1874
- 1981. Because it deals only with the evolution of
individual BMRs the model includes only destruction of open
flux at the BMR polarity reversal and not that at neutral
lines between individual BMRs when more than one is
present. The reconstruction makes use of the greenwich
records of the appearance of sunspot groups and the model is
then used along with the group latitude and umbral area to
predict how the open flux would evolve if there was no
inter-BMR loss. Using a super-posed epoch technique we
compare the average evolution of sunspot area with that
predicted by the model the differnce telling us about the
effect of loss of total flux at inter-BMR neutral
lines. From this we can correct the predicted open flux
variation to allow for the effect of the inter-BMR neutral
lines. The interval of the greenwich data is important
because we can compare the results with the open flux
variations calculated by Lockwood et al. [1999].}
}
@article{2006RaSc...41S6012F,
author = {Fotiadis, D.N. and Kouris, S.S.},
title = {Capturing the morphology of long-duration negative
ionospheric disturbances using an empirical pattern
recognition method},
journal = {Radio Science},
year = 2006,
month = dec,
volume = 41,
pages = {6012-+},
doi = {10.1029/2005RS003395},
adsurl = {http://adsabs.harvard.edu/abs/2006RaSc...41S6012F},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {On the basis of an ionospheric definition of disturbed
conditions independent of any causative mechanism, a
feature-guided pattern recognition method reveals the
dominant morphology of long-duration negative foF2
disturbances. A catalogue of negative disturbances lasting
more than 24 hours is compiled from hourly foF2 data from 75
ionosonde stations and three solar cycles. Disturbances in
each month and station are handled separately, and four
local time intervals of disturbance commencement are
considered. A median disturbance profile is produced only
when a minimum occurrence probability holds. The time window
under morphological investigation is selected such that
nonsystematic features, precursor phenomena, and poststorm
effects are not included in analysis. The disturbance
patterns, first grouped according to major characteristic
features and then fitted with simple mathematic functions,
are described by a range of the normalized deviation of
hourly foF2 to its corresponding monthly median and are
provided to radio users along with their distribution in
space and time. The present model is a nonconditional
stand-alone model which may, in the event of an ionospheric
disturbance at a certain location, predict its further
development.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{francis01:_predic,
author = {Francis, N.M. and Brown, A.G. and Cannon, P.S. and
Broomhead, D.S.},
title = {Prediction of the hourly ionospheric parameter, foF2,
incorporating a novel nonlinear interpolation technique to
cope with missing data points},
journal = {Journal of Geophysical Research},
pages = {30077-30084},
year = {2001},
month = {dec},
volume = {106},
number = {A12},
url = {http://dx.doi.org/10.1029/2000JA002227},
abstract = {A technique for neural network time series prediction using
radial basis functions, where the input data contain a
significant proportion of missing points, is developed. This
technique is intended to model the data while simultaneously
providing a means of minimizing the impact upon the model of
the missing points that are typical of geophysical time
series. The two issues are inextricably entwined because
missing data points have a significant impact upon the
performance of data-derived models in terms of prediction
availability and accuracy. The core of the technique is a
nonlinear interpolation scheme that assigns values to gaps
in the input time series. Each missing point is interpolated
such that the error introduced into any specific predictive
function is minimized. This interpolative technique has a
general application in any instance where the effects of
interpolation upon a given analysis process need to be
minimized or a complete time series needs to be constructed
from incomplete data. The technique has been applied to the
prediction of fOF2 from Slough, United Kingdom. The
resultant model prediction root-mean-square (RMS) error is
shown to be 2.3\% better than using recurrence interpolation
(in terms of overall model accuracy rather than relative to
each other), 3.8\% better than using persistence
interpolation, and 34.3\% better than not using any
interpolation. Utilizing the interpolation algorithm lowers
the RMS error by 26\% when incomplete data, in addition to
complete data, are used as an input to both the interpolated
and the uninterpolated models.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{fraser05:_new_zealan,
author = {Fraser, G.J.},
title = {The antecedents and subsequent development of scientific
radar in New Zealand},
journal = {jastp},
year = 2005,
volume = 67,
number = 15,
pages = {1411--1418},
month = {October},
ukssdc_d = {},
url = {http://dx.doi.org/10.1016/j.jastp.2005.07.010},
abstract = {In New Zealand after World War 2 radar techniques were used
in various investigations in geophysics and astronomy. Much
local expertise had become available from defence
laboratories, which had been set up in 1939 and eventually
merged into the Radio Development Laboratory, disbanded in
1946. Wartime radar development had in turn been founded on
pre-war research in radio propagation and ionospheric
research which included the use of pulse
ionosondes. Frequent support for the pre-war radio research
in both Britain and New Zealand was given by Ernest
Rutherford who, throughout his life, retained the interest
from his own early researches in radio wave
propagation. This paper is a brief survey of events from
Rutherford's early experiments in 1894 to present-day
research programmes.}
}
@article{fuller-rowell00:_empir_storm_time_correc_model,
author = {Fuller-Rowell, T.J. and Araujo-Pradere, E.A. and Codrescu,
M.V.},
title = {An Empirical Storm-Time Correction Model},
journal = {Advances in Space Research},
pages = {139--146},
year = {2000},
volume = {25},
number = {1},
abstract = {An empirical model for F-region peak ionospheric storm-time
changes has been developed based on understanding from
theoretical modeling of geomagnetic storms. The model is
designed to scale climatology, or monthly-medians, based on
the strength of a storm, as a function of geomagnetic
latitude, season, and local time. The model is driven by an
index derived from the previous thirty hours of auroral or
geomagnetic activity, suitably weighted by a filter. The
model is particularly effective in capturing the ionospheric
storm negative phase in summer mid latitudes, where it
reduces the root-mean-square error by more than a factor of
two. The winter mid-latitude F region typically experiences
a positive phase during a storm accompanied by a high degree
of variability. The model does less well in these
circumstances but still makes a significant reduction in the
variance. The ionospheric storm-time model can be used to
scale monthly median values or a quiet time model such as
the International Reference Ionosphere.},
ukssdc_d = {},
uk_first = {}
}
@article{garcia-fernandez2003,
author = {Garcia-Fernandez, M. and Hernandez-Pajares, M. and Juan,
J.M. and Sanz, J. and Orus, R. and Coisson, P. and Nava,
B. and Radicella, S.M.},
title = {Combining ionosonde with ground GPS data for electron
density estimation},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2003},
volume = {65},
number = {6},
pages = {683--691},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Dual frequency Global Positioning System (GPS) receivers
provide integrated total electron content (TEC) along the
ray path (slant TEC, affected by a bias). By inverting this
observable, it is possible to obtain the vertical total
electron content with some assumptions about the horizontal
structure of the ionosphere. The large number of permanent
receivers distributed around the world provide enough
information to obtain such TEC observables with high spatial
and temporal resolutions. Nevertheless, the geometry (mainly
vertical) of the ground GPS observations does not allow to
solve the vertical structure of electron density of the
ionosphere. Mixing different kinds of complementary data in
a tomographic context helps to overcome this
problem. Several works have obtained successful results
achieved by combining occultation and ground GPS data to
estimate the local three-dimensional structure of
ionospheric electron density. This paper proposes the use of
just ground data to obtain similar or better results. To do
this, the ground GPS data are mixed with vertical profiles
of electron density derived from ionosonde data instead of
GPS occultation observations. In this paper, the
complementarity between vertical profiles of electron
density (estimated using the NeQuick model) and ground GPS
data (from GPS IGS permanent network) are shown as well as
the performance of the resulting combination.}
}
@article{2006RaSc...41S6S08G,
author = {Garner, T.W. and Bust, G.S. and Gaussiran, T.L. and Straus,
P.R.},
title = {Variations in the midlatitude and equatorial ionosphere
during the October 2003 magnetic storm},
journal = {Radio Science},
year = 2006,
month = dec,
volume = 41,
pages = {6-+},
doi = {10.1029/2005RS003399},
adsurl = {http://adsabs.harvard.edu/abs/2006RaSc...41S6S08G},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {The October 2003 geomagnetic storm (often called the
Halloween storm) was one of the largest storms (as measured
by Dst) yet recorded. The storm-induced synoptic-scale
changes in the ionosphere's plasma content and density can
be viewed through space weather maps created by objective
analysis algorithms. For this study, these maps, which
specify the electron density in altitude, latitude, and
longitude, are created by the ionospheric data assimilation
three dimensional (IDA3D), a three-dimensional variation
algorithm of the ionospheric electron density. These maps,
representing the average conditions in the ionosphere over a
15 min sampling time, show how dramatically the ionosphere
changed during the Halloween storm. Following the southward
turning of the interplanetary magnetic field, the dayside
electron content is significantly reduced in the equatorial
ionosphere between $\pm18^{\circ}$ magnetic latitude and is
enhanced poleward of this latitude. This is the expected
behavior when the equatorial fountain is enhanced by a
strong penetration electric field. In addition, the electron
content is significantly increased in the dayside
midlatitude ionosphere, which corresponds to a
storm-enhanced density (SED) plume. Above $40^{\circ}$
magnetic latitude, the dayside plasma content is
significantly reduced in the regions adjacent to the SED
structure, which enhances the electron content
gradient. Electron density maps in the altitude-magnetic
latitude plane show an increase in the topside electron
densities within an SED plume.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{gilbert1988,
author = {Gilbert, John D. and Smith, Richard W.},
title = {A comparison between the automatic ionogram scaling system
ARTIST and the standard manual method},
journal = {Radio Science},
pages = {968--974},
year = {1988},
month = nov,
volume = {23},
number = {6},
abstract = {Data from midlatitude ionograms scaled by the computer
system, ARTIST, are compared with data from the standard
manual method. Differences between the scaled values for
foF2 and M(3000)F2 are presented for five periods of low
sunspot activity between 1984 and 1986. It is found that the
ARTIST system provides acceptable data about 93 pct of the
time. The system does not perform as well in summer due to
the presence of blanketing-type Es and the proximity of foF2
to foF1.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{griffin01:_solar,
author = {Griffin, E.M. and Aruliah, A.L.},
title = {Solar cycle differences in mid-latitude meridional
thermospheric neutral wind climatologies},
journal = {Annales Geophysicae},
pages = {863-876},
year = {2001},
month = mar,
volume = {22},
number = {3},
abstract = {The climatological behaviour of the thermospheric meridional
wind above Kiruna, Sweden ($67.4^{\circ}$N, $20.4^{\circ}$E)
has been investigated for seasonal and solar cycle
dependence using six different techniques, comprising both
model and experimental sources. Model output from both the
empirical Horizontal Wind Model (HWM) (Hedin et al., 1988)
and the numerical Coupled Thermosphere and Ionosphere Model
(CTIM) are compared to the measured behaviour at Kiruna, as
a single site example. The empirical International Reference
Ionosphere (IRI) model is used as input to an implementation
of servo theory, to provide another climatology combining
empirical input with a theoretical framework. The
experimental techniques have been introduced in a companion
paper in this issue and provide climatologies from direct
measurements, using Fabry-Perot Interferometers (FPI),
together with 2 separate techniques applied to the European
Incoherent Scatter radar (EISCAT) database to derive neutral
winds. One of these techniques uses the same implementation
of servo theory as has been used with the IRI
model. Detailed comparisons for each season and solar
activity category allow for conclusions to be drawn as to
the major influences on the climatological behaviour of the
wind at this latitude. Comparison of the incoherent scatter
radar (ISR) derived neutral winds with FPI, empirical model
and numerical model winds is important to our understanding
and judgement of the validity of the techniques used to
derive thermospheric wind databases. The comparisons also
test model performance and indicate possible reasons for
differences found between the models. In turn, the
conclusions point to possible improvements in their
formulation. In particular it is found that the empirical
models are over-reliant on mid-latitude data in their
formulation, and fail to provide accurate estimates of the
winds at high-latitudes.},
ukssdc_d = {},
uk_first = {}
}
@article{gulyaeva05:_night,
author = {Gulyaeva, T. and Stanislawska, W.},
title = {Night-day imprints of ionospheric slab thickness during
geomagnetic storm},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = 2005,
volume = 67,
number = 14,
pages = {1307--1314},
month = {September},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1016/j.jastp.2005.07.006},
abstract = {Spatial maps of the ionosphere-plasmasphere slab thickness
(T) were generated as a ratio of the total electron content
(TEC) to the F-region peak electron density (NmF2) at 1
degrees spaced grid points from the instantaneous maps of
TEC and foF2 at latitudes 35 degrees to 70 degrees N, and
longitudes -10 degrees to 40 degrees E. Data of 23
observatories are used for the construction of TEC and foF2
maps with Kriging technique from independent networks of
GPS-TEC and ionosonde observations at solar minimum
(1995-1996) and maximum (2002) under quiet and disturbed
magnetic conditions. The net-weight factor (omega) is
introduced as a ratio of disturbance to quietness
representing area mean TEC,foF2 and tau for a particular day
and time normalized by relevant monthly median
value. Analysis of w evolution for TEC, foF2 and T maps have
revealed that TEC and foF2 depletion is accompanied by
positive increment of slab thickness for more than 48 hrs
during the magnetic storm at solar maximum but T enhancement
is shorter and delayed by 12 to 24 hrs regarding the storm
onset at solar minimum. The slab thickness positive
increment at the main,phase of geomagnetic storm has been
associated with relevant increase of the real thickness of
the topside ionosphere. To estimate-the upper boundary of
the ionosphere the International Reference Ionosphere
expanded towards the plasmasphere (IRI*) is modified to
assimilate the ionosonde F2 layer peak and the GPS-T.EC
observations. Slab thickness is decomposed in three parts
(the bottomside and topside ionosphere, and the
plasmasphere). Eliminating the plasmasphere part from the
total slab thickness, we obtain the ratio of bottomside slab
thickness to the real thickness below the F2 layer
peak. Assuming that this ratio is also valid above the F2
layer peak, we obtain the topside boundary of the ionosphere
varying from 500 km by day to 2300km by night.}
}
@article{2007JATP...69..528G,
author = {Gulyaeva, T.L.},
title = {{Variable coupling between the bottomside and topside
thickness of the ionosphere}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2007,
month = apr,
volume = 69,
pages = {528-536},
doi = {10.1016/j.jastp.2006.10.015},
adsurl = {http://adsabs.harvard.edu/abs/2007JATP...69..528G},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
ukssdc_i = {}
}
@article{gulyaeva01:_forec,
author = {Gulyaeva, T.L.},
title = {Forecasting of recurrent magnetic storms 1 day in advance},
journal = {Geomagn. and Aeronomy},
year = {2002},
pages = {159-164},
volume = {29},
ukssdc_d = {}
}
@article{gulyaeva1993,
author = {Gulyaeva, T.L.},
title = {Indices of geomagnetic variations and ionospheric
disturbances},
journal = {Advances in Space Research},
pages = {29-31},
year = {1993},
volume = {13},
number = {3},
abstract = {In December 1990 a new IRI handbook was published by NASA's
National Space Science Data Center (NSSDC) describing in
detail the International Reference Ionosphere 1990. Shortly
thereafter, the IRI-90 software was released on tape,
diskette, and computer networks. This paper is intended as
an inventory of the most important IRI activities up to 1990
and as a starting point for the next improvement cycle. It
summarizes the work and studies that led to IRI-90 and
provides an overview over this latest version of the
model. Shortcomings and limitations are pointed out and ways
of overcoming them are discussed. Priorities are suggested
for the list of work items that the IRI group has to tackle
in the future. High on the wish-list are (i) major
improvements at high latitudes and (ii) inclusion of
magnetic storm effects. This paper deals with plasma
temperatures, ion composition, and ion drift; the preceding
companion paper discusses the electron density. },
ukssdc_d = {}
}
@inproceedings{gulyaeva1993b,
author = {Gulyaeva, T.L.},
title = {Vertical incidence sounding database and its products},
booktitle = {Proceedings of XXIV URSI General Assembly},
organization = {URSI},
year = {1993},
month = aug,
address = {Kyoto, Japan},
ukssdc_d = {}
}
@article{gulyaeva01:_elect_f2_septem,
author = {Gulyaeva, T.L. and De Franceschi, G. and Perrone, L.},
title = {Electron temperature variations at the F2 layer peak height
during the space weather month of September 1999},
journal = {Advances in Space Research},
year = {2001},
pages = {965-970},
month = sep,
volume = {31},
number = {4},
abstract = {Data from 23 ionospheric stations are used for September
1999 to produce the electron temperature, Te, at the F2
layer peak height, hmF2, on the base of empirical relation
between Te and the electron density, Ne, at a given height
for a given index of solar radio flux (Brace and Theis,
1978, 1984). Daily and monthly Te minimum, mean, and maximum
are then evaluated for each station. Near the solar maximum
monthly Te(min) is about 1470K while the monthly
Te(max), occurring during sunrise, varies with location in a
wide range from 1900 to 3900K. A new weighted scheme
is suggested for forecast of magnetic activity 3 h in
advance by accumulation of selected magnetic indices ranked
by decreasing order for 12 hrs preceding given time of
observation. By using the daily Te values, cold and hot
ionospheric days during the month have been defined: the
magnetic activity does not influence Te at low and
equatorial latitudes while at mid-latitudes a high degree of
correlation is found between the F2 peak plasma heating and
weighted accumulation of the magnetic indices. The most
important effect of Te heating at sunrise is observed at
high latitudes during the recovery phase of magnetic storm
and sub-storm.},
ukssdc_d = {}
}
@inproceedings{gulyaeva01:_gps_tec_nmf2,
author = {Gulyaeva, T.L. and Jakowski, N.},
title = {A linear regression model between GPS-TEC and NmF2
variability indices},
booktitle = {Proc. of the International Workshop on Space Weather Effects
on Satellite Signals},
year = {2001},
address = {Boston, MA, USA},
ukssdc_d = {}
}
@article{gulyaeva01:_dynam,
author = {Gulyaeva, T.L. and Mahajan, K.K.},
title = {Dynamic boundaries of the ionosphere variability},
journal = {Advances in Space Research},
pages = {91--94},
year = {2001},
volume = {27},
number = {1},
abstract = {It has been shown that the conventional threshold of +/-20\%
departures from monthly median cannot serve for reliably
distinguishing quiet and disturbed ionospheric conditions at
different latitudes/time-of-day/season/level of solar
activity. After a 3 h filtering of daily-hourly foF2
critical frequency, for each 3 h UT bin new upper and lower
variability boundaries are introduced, based on the extreme
foF2 values normalized to the monthly median similar to
assessments of warming-cooling of air temperature in
meteorology. Application of so defined boundaries is made to
long-term observations at 56 ionospheric stations world-wide
for the period of 1942 to 1999 comprising in total more than
13,000,000 hourly foF2 values.},
ukssdc_d = {}
}
@article{hapgood1991,
author = {Hapgood, M.A. and Lockwood, M. and Bowe, G.A. and Willis,
D.M. and Tulunay, Y.K.},
title = {Variability of the interplanetary medium at 1 a.u. over 24
years: 1963--1986},
journal = {Planetary and Space Science},
pages = {411--423},
year = {1991},
month = mar,
volume = {39},
number = {3},
abstract = {A survey is presented of hourly averages of observations of
the interplanetary medium, made by satellites close to the
Earth (i.e. at 1 a.u.) in the years 1963-1986. This survey
therefore covers two complete solar cycles (numbers 20 and
21). The distributions and solar-cycle variations of IMF
field strength, $B$, and its northward component (in GSM
coordinates), $B_{z}$, and of the solar-wind density, n,
speed, $\upsilon$, and dynamic pressure, P, are
discussed. Because of their importance to the terrestrial
magnetosphere/ionosphere, particular attention is given to
$B_{z}$ and P. The solar-cycle variation in the magnitude
and variability of $B_{z}$, previously reported for cycle
20, is also found for cycle 21. However, the solar-wind data
show a number of differences between cycles 20 and 21. The
average dynamic pressure is found to show a solar-cycle
variation and a systematic increase over the period of the
survey. The minimum of dynamic pressure at sunspot maximum
is mainly due to reduced solar-wind densities in cycle 20,
but lower solar-wind speed in cycle 21 is a more significant
factor. The distribution of the duration of periods of
stable polarity of the IMF $B_{z}$ component shows that the
magnetosphere could achieve steady state for only a small
fraction of the time and there is some evidence for a
solar-cycle variation in this fraction. It is also found
that the polarity changes in the IMF $B_{z}$ fall into two
classes: one with an associated change in solar-wind dynamic
pressure, the other without such a change. However, in only
20\% of cases does the dynamic pressure change exceed 50\%.},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{heaton2001,
author = {Heaton, J.A.T. and Cannon, P.S. and Rogers, N.C. and
Mitchell, C.N. and Kersley, L.},
title = {Validation of electron density profiles derived from oblique
ionograms over the United Kingdom},
journal = {Radio Science},
year = {2001},
volume = {36},
number = {5},
pages = {1149--1156},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
url = {http://dx.doi.org/10.1029/1999RS002423},
abstract = {Inversion algorithms are available to derive the vertical
electron density profile at the midpoint of an oblique
sounder path. The techniques open up the possibility of
monitoring the ionosphere at otherwise inaccessible
locations, such as over sea or inhospitable terrain. A new
method of monitoring the ionosphere based on radio
tomography can be used to create two-dimensional images of
electron density. The results in this paper compare midpoint
profiles derived from oblique ionograms with corresponding
profiles obtained from tomographic images of electron
density and from a vertical ionospheric sounder. The
comparisons illustrate the oblique sounder inversion
technique and its inherent limitations. The results provide
useful information on the complementary nature of the
separate ionospheric measurement techniques and have
implications for the use of these measurements as inputs to
real-time ionospheric models.}
}
@article{hernandez-pajares00:_improv_abel_gps_leo,
author = {Hernandez-Pajares, M. and Juan, J.M. and Sanz, J.},
title = {Improving the Abel inversion by adding ground GPS data to
LEO radio occultations in ionospheric sounding},
journal = {Geophysical Research Letters},
year = 2000,
volume = 27,
number = 16,
pages = {2473--2476},
month = aug,
url = {http://maite152.upc.es/manuel/reprints/GL10736W01.pdf},
ukssdc_d = {},
abstract = {GPS radio occultations allow the sounding of the Earth's
atmosphere (i.e. troposphere and ionosphere). The basic
observable of this technique is the additional delay, due to
the refractivity index, of a radio signal when passing
through the atmosphere. This additional delay is
proportional to the integrated refractivity, in such a way
that we can obtain an estimation of the vertical
refractivity profiles using observations at different
elevation angles by solving an inverse
problem. Traditionally, the solution of this inverse problem
is obtained by using the Abel inversion algorithm assuming a
refractivity index that only depends on the altitude. In
this paper we present a modified Abel inversion algorithm
for ionospheric sounding that overcomes the spherical
symmetry assumption of the traditional Abel inversion
algorithm. Processing a set of simulated data and 1 day of
real data with this algorithm, a clear improvement over the
traditional one can be obtained when comparing the derived
critical frequencies with the ionosonde measurements. It is
also shown that this improvement is sufficient to measure
critical frequencies associated with the ionospheric E
layer.}
}
@techreport{rs1982,
author = {Hewish, A. and others},
title = {Synoptic data for Solar-Terrestrial Monitoring},
institution = {The Royal Society},
year = {1992},
month = sep,
address = {London},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{ivanov-kholodnyi2000,
author = {Ivanov-Kholodnyi, G.S. and Chertoprud, V.E.},
title = {Peculiarities of solar-ionospheric relationships during
minima and maxima of 27-day variations in $F_{10.7}$},
journal = {Annales Geophysicae},
year = {2000},
volume = {40},
number = {6},
pages = {681--686},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Based on a 37-year-long (1958-1994) series of hourly
measurements of the ionospheric E-region critical frequency
$f_{o}E$ at four stations (Moscow, Kaliningrad, Slough, and
Boulder), we determine the ionization index $I_{E}$ (the
fourth power of the normalized critical frequency) and
analyze its correlation with solar radio flux $F_{10.7}$
during maxima and minima of 27-day variations in $F_{10.7}$
The coefficients of the linear regression equation that
describes the correlation of $I_{E}$ with $F_{10.7}$ have
been found to differ markedly during these periods and
exhibit semiannual variations. Possible causes of these
effects are discussed.}
}
@article{jarvis2002,
author = {Jarvis, M.J. and Clilverd, M.A. and Ulich, T.},
title = {Methodological influences on F-region peak height trend
analyses},
journal = {Physics and Chemistry of the Earth},
year = {2002},
volume = {27},
number = {6--8},
pages = {589--594},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {Published estimates of the trend in hmF2 using data from
ionosondes over the last 30-40 years range from +0.8 to -0.6
km yr$^{-1}$ and are subject to the influence of several
factors. These are considered here based upon an analysis of
two southern hemisphere geomagnetically mid-latitude
stations, Argentine Islands and Port Stanley. The influence
of the equation used to calculate hmF2 at these stations can
result in variations of $\pm0.2$ km yr$^{-1}$; choice of solar
proxy has a small influence on the end result, where using
E10.7 instead of F10.7 produces changes of -0.04 km
yr$^{-1}$; neglecting any trends in geomagnetic activity can
produce variations of +0.03 to +0.2 km yr$^{-1}$ at the two
mid-latitude stations considered in this paper; for datasets
of 30-40 years length ringing due to long memory processes
can produce $\pm0.2$ km yr$^{-1}$ variability; the phase of the
11-year solar cycle, and its harmonics, captured by the
datasets can cause variability of $\pm0.5$ km yr$^{-1}$; and the
neglect of local time variations in thermospheric wind
conditions could result in +0.2 km yr$^{-1}$ for analysis which
only considers local midday data. The Argentine Islands and
Port Stanley datasets show ringing terms that are still
converging towards trend results of -0.25 to -0.30 km
yr$^{-1}$, which are in close agreement with the satellite drag
trend estimates.}
}
@article{jarvis98:_south_f,
author = {Jarvis, M.J. and Jenkins, B. and Rodgers, G.A.},
title = {Southern hemisphere observations of a long-term decrease in
F region altitude and thermospheric wind providing possible
evidence for global thermospheric cooling},
journal = {Journal of Geophysical Research},
pages = {20775--20787},
year = {1998},
volume = {103},
number = {A9},
abstract = {F-region peak heights, derived from ionospheric scaled
parameters through 38-year data series from both Argentine
Islands (65 S, 64 W) and Port Stanley (52 S, 58 W) have been
analysed for signatures of secular change. Long-term changes
in altitude, which vary with month and time of day, were
found at both sites. The results can be interpreted either
as a constant decrease in altitude combined with a
decreasing thermospheric wind effect, or a constant decrease
in altitude which is altitude-dependent. Both
interpretations leave inconsistencies when the results from
the two sites are compared. The estimated long-term decrease
in altitude is of a similar order of magnitude to that which
has been predicted to result in the thermosphere from
anthropogenic change related to greenhouse gases. Other
possibilities should not, however, be ruled out.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{jiping95:_time_weigh,
author = {Jiping, Wu. and Wilkinson, P.J.},
title = {Time Weighted magnetic indices as predictors of ionospheric
behaviour},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {1763--1770},
year = {1995},
month = {dec},
volume = {57},
number = {14},
abstract = {A time-weighted accumulation of the ap index, ap(small tau,
Greek) (Wrenn, 1987; Wrenn et al., 1987, 1989), together
with other similar indices, was explored as a predictor of
ionospheric behaviour, using f$_{o}$F2 data for a selection of
locations in Australia and Europe for September and October
1989. All the time accumulated indices showed improved
linear correlations, indicative of a response time of the
order of about 15 hours. The response time could be
decomposed into a lag between respective time series and a
persistence time, although the decomposition appeared
unnecessary as the persistence time carried the same
information. Of the individual indices investigated,
aa(small tau, Greek) appeared best and the auroral oval
equatorward edge index (AI index) was poorest, although the
differences were not statistically significant. Comparisons
between the aa, ap and Kp indices, plus comparisons between
different ionospheric parameters showed that forecasting may
be improved using different transformations of the
data. While these results appear good, further studies using
other stations and seasons are warranted to confirm their
utility for forecasting.},
ukssdc_d = {}
}
@article{2006GeoRL..3307811J,
author = {Johnson, C.G. and Davis, C.J.},
title = {{The location of lightning affecting the ionospheric
sporadic-E layer as evidence for multiple enhancement
mechanisms}},
journal = {Geophysical Research Letters},
year = 2006,
month = apr,
volume = 33,
pages = {7811-+},
doi = {10.1029/2005GL025294},
adsurl = {http://adsabs.harvard.edu/abs/2006GeoRL..3307811J},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {We present a study of the geographic location of lightning
affecting the ionospheric sporadic-E (Es) layer over the
ionospheric monitoring station at Chilton, UK. Data from the
UK Met Office's Arrival Time Difference (ATD) lightning
detection system were used to locate lightning strokes in
the vicinity of the ionospheric monitoring station. A
superposed epoch study of this data has previously revealed
an enhancement in the Es layer caused by lightning within
200km of Chilton. In the current paper, we use the same data
to investigate the location of the lightning strokes which
have the largest effect on the Es layer above Chilton. We
find that there are several locations where the effect of
lightning on the ionosphere is most significant
statistically, each producing different ionospheric
responses. We interpret this as evidence that there is more
than one mechanism combining to produce the previously
observed enhancement in the ionosphere.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{jones04,
author = {Jones, T. B. and Wright, D. M. and Milner, J. and Yeoman,
T. K. and Reid, T. and Senior, A. and Martinez, P.},
title = {The detection of atmospheric waves produced by the total
solar eclipse 11 August 1999},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
pages = {363-374},
year = {2004},
month = mar,
volume = {66},
number = {5},
abstract = {In previous attempts to detect eclipse-induced AGW, it has
always been difficult to establish a direct link between
individual waves and a specific source. This study reports
observations of travelling ionospheric disturbances made in
the UK at the time of the total solar eclipse of 11 August
1999. The speed and direction of the waves were estimated by
a four-station array using the HF Doppler technique. In
addition, the wave observations were supported by two other
propagation paths, one in the north of England close to the
main array and the other further afield, between the UK and
Sweden. The AGW activity following the eclipse totality was
different to the background waves detected before this time
in amplitude, speed and direction. The velocity vectors are
consistent with a generating mechanism for the waves based
on the supersonic passage of the cooled region of the
atmosphere during the eclipse.},
ukssdc_i = {},
ukssdc_d = {},
uk_first = {}
}
@article{kalinin2003,
author = {Kalinin, U.K. and Romanchuk, A.A. and Sergeenko, N.P. and
Shubin, V.N.},
title = {The large-scale isolated disturbances dynamics in the main
peak of electronic concentration of ionosphere},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2003},
volume = {65},
number = {11--13},
pages = {1175--1177},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The vertical sounding data at chains of ionosphere stations
are used to obtain relative variations of electron
concentration in the F2 ionosphere region. Specific isolated
traveling large-scale irregularities are distinguished in
the diurnal succession of the f$_{o}$F2 relative variations
records. The temporal shifts of the irregularities at the
station chains determine their motion velocity (of the order
of speed of sound) and spatial scale (of order of 3000-5000
kin, the trajectory length being up to 10000 km). The motion
trajectories of large-scale isolated irregularities which
had preceded the earthquakes are reconstructed.}
}
@article{2006JATP...68..877K,
author = {Kane, R.P.},
title = {{Are the double-peaks in solar indices during solar maxima
of cycle 23 reflected in ionospheric foF2?}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2006,
month = may,
volume = 68,
pages = {877-880},
doi = {10.1016/j.jastp.2006.02.003},
adsurl = {http://adsabs.harvard.edu/abs/2006JATP...68..877K},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
ukssdc_i = {}
}
@article{karlsson00:_solar,
author = {Karlsson, S.~B.~P. and Opgenoorth, H.~J. and Eglitis,
P. and Kauristie, K. and Syrj\"asuo, M. and
Pulkkinen, T. and Lockwood, M. and Nakamura, R. and
Reeves, G. and Romanov, S.},
title = {Solar wind control of magnetospheric energy content:
Substorm quenching and multiple onsets},
journal = {Journal of Geophysical Research},
year = 2000,
month = mar,
volume = 105,
number = 14,
pages = {5335-5356},
url = {http://dx.doi.org/10.1029/1999JA900297},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2000JGR...105.5335K&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
uk_other = {},
ukssdc_d = {},
abstract = {In this paper we report coordinated multispacecraft and
ground-based observations of a double substorm onset close
to Scandinavia on November 17, 1996. The Wind and the
Geotail spacecraft, which were located in the solar wind and
the subsolar magnetosheath, respectively, recorded two
periods of southward directed interplanetary magnetic field
(IMF). These periods were separated by a short northward IMF
excursion associated with a solar wind pressure pulse, which
compressed the magnetosphere to such a degree that Geotail
for a short period was located outside the bow shock. The
first period of southward IMF initiated a substorm growth
phase, which was clearly detected by an array of
ground-based instrumentation and by Interball in the
northern tail lobe. A first substorm onset occurred in close
relation to the solar wind pressure pulse impinging on the
magnetopause and almost simultaneously with the northward
turning of the IMF. However, this substorm did not fully
develop. In clear association with the expansion of the
magnetosphere at the end of the pressure pulse, the auroral
expansion was stopped, and the northern sky cleared. We will
present evidence that the change in the solar wind dynamic
pressure actively quenched the energy available for any
further substorm expansion. Directly after this period, the
magnetometer network detected signatures of a renewed
substorm growth phase, which was initiated by the second
southward turning of the IMF and which finally lead to a
second, and this time complete, substorm intensification. We
have used our multipoint observations in order to understand
the solar wind control of the substorm onset and substorm
quenching. The relative timings between the observations on
the various satellites and on the ground were used to infer
a possible causal relationship between the solar wind
pressure variations and consequent substorm
development. Furthermore, using a relatively simple
algorithm to model the tail lobe field and the total tail
flux, we show that there indeed exists a close relationship
between the relaxation of a solar wind pressure pulse, the
reduction of the tail lobe field, and the quenching of the
initial substorm.}
}
@article{kavanagh04:_statis,
author = {Kavanagh, A. J.and Kosch, M. J. and Honary, F. and Senior,
A. and Marple, S. R. and Woodfield, E. E. and McCrea, I. W.},
title = {Statistical dependence of auroral absorption on geomagnetic
and solar wind parameters},
journal = {Annales Geophysicae},
pages = {877-887},
year = 2004,
volume = 22,
number = 3,
abstract = {Data from the Imaging Riometer for Ionospheric Studies
(IRIS) at Kilpisjarvi, Finland, have been compiled to form
statistics of auroral absorption based on seven years of
observations. By splitting the absorption into eight
magnetic local time (MLT) sectors empirical relationships
between observations of precipitation and geomagnetic
activity are obtained. Through the use of in-situ
measurements of the solar wind (from the Wind and ACE
satellites) a linear relationship between the solar wind
velocity and the cosmic noise absorption in the auroral zone
is also derived. A dependence on the southward IMF
(Interplanetary Magnetic Field) is demonstrated with
absorption increasing with successive decreases in B$_{z}$;
a northward IMF appears to have little effect and neither
does the eastward component, B$_{y}$.},
ukssdc_d = {},
uk_first = {}
}
@article{king1973,
author = {King, J.W.},
title = {Solar radiation changes and the weather},
journal = {Nature},
pages = {443--446},
year = {1973},
month = oct,
volume = {245},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{knipp98:_novem,
author = {Knipp, D.J. and Emery, B.A. and Engebretson, M. and Li,
X. and McAllister, A.H. and Mukai, T. and Kokubun, S. and
Reeves, G.D. and Evans, D. and Obara, T. and Pi, X. and
Rosenberg, T. and Weatherwax, A. and McHarg, M.G. and Chun,
F. and Mosely, K. and Codrescu, M. and Lanzerotti, L. and
Rich, F. and Sharber, J. and Wilkinson, P.},
title = {An overview of the early November 1993 geomagnetic storm},
journal = {Journal of Geophysical Research},
pages = {26197-26220},
year = {1998},
volume = {103},
number = {A11},
abstract = {This paper describes the development of a major space storm
during November 2-11, 1993. We discuss the history of the
contributing high-speed stream, the powerful combination of
solar wind transients and a corotating interaction region
which initiated the storm, the high-speed flow which
prolonged the storm and the near-Earth manifestations of the
storm. The 8-day storm period was unusually long; the result
of a high-speed stream (maximum speed 800 km/s) emanating
from a distended coronal hole. Storm onset was accompanied
by a compression of the entire dayside magnetopause to
within geosynchronous Earth orbit (GEO). For nearly 12 hours
the near-Earth environment was in a state of tumult. A
super-dense plasma sheet was observed at GEO, and severe
spacecraft charging was reported. The effects of electrons
precipitating into the atmosphere penetrated into the
stratosphere. Subauroral electron content varied by 100% and
F layer heights oscillated by 200 km. Equatorial plasma
irregularities extended in plumes to heights of 1400
km. Later, energetic particle fluxes at GEO recovered and
rose by more than an order of magnitude. A satellite anomaly
was reported during the interval of high energetic electron
flux. Model results indicate an upper atmospheric
temperature increase of 200K within 24 hours of storm
onset. Joule heating for the first 24 hours of the storm was
more than 3 times that for typical active geomagnetic
conditions. We estimate that total global ionospheric
heating for the full storm interval was ~190 PJ, with 30\%
of that generated within 24 hours of storm onset.},
ukssdc_d = {}
}
@article{korenkov2002,
author = {Korenkov, Y.N. and Klimenko, V.V. and Bessarab, F.S. and
Ferster, M.},
title = {Modeling of the ionospheric F2-region parameters in quiet
conditions on January 21-22, 1993},
journal = {Annales Geophysicae},
year = {2002},
volume = {42},
number = {3},
pages = {350--359},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Results of the simulation of ionospheric parameters over
American stations (Millstone Hill, Arecibo, Port Stanley,
and the Argentine Islands) and the European EISCAT station
are presented. The calculations have been performed with the
help of the global self-consistent model of the
thermosphere, ionosphere, and protonosphere (GSM TIP) for
January 21, 1993. The day considered, entering into the
LTCS-9 campaign period, was characterized by quiet
geomagnetic conditions and moderate solar activity. It is
shown that the calculated and observed values of foF2 and
T$_{e}$ agree satisfactorily if we take into account soft
electron precipitation in the diffuse zone, located
equatorward of the main auroral precipitation zone, and in
the South American geomagnetic anomaly zone.}
}
@article{kouris98:_solar_m_f2,
author = {Kouris, S.S. and Bradley, P.A. and Dominici, P.},
title = {Solar-cycle variation of the daily foF2 and M(3000)F2},
journal = {Annales Geophysicae},
pages = {1039--1042},
year = {1998},
volume = {16},
number = {8},
abstract = {Daily values of the ionospheric characteristics foF2 and
M(3000)F2 for a given hour and month are correlated with the
corresponding daily values of sunspot number using measured
data collected at seven European locations. The significance
of applying different-order polynomials is considered and
the times are confirmed when the higher-order terms are
important. Mean correlation coefficients for combined data
sets over all hours, months and stations are determined,
together with the standard errors of estimates. Comparisons
are made with corresponding figures for monthly median
values derived from the same data sets.},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{krasnov2003,
author = {Krasnov, V.M. and Drobzheva, Y.V. and Venart, J.E.S. and
Lastovicka, J.},
title = {A re-analysis of the atmospheric and ionospheric effects of
the Flixborough explosion},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2003},
volume = {65},
number = {11--13},
pages = {1205--1212},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The ionospheric record of the 1974 cyclohexane vapour cloud
explosion (VCE) accident near Flixborough is re-examined in
light of a new theory used to describe the acoustic field in
the atmosphere and ionosphere caused by explosions on the
ground. The reconstructed oblique Doppler sounding records
from six radio traces agree remarkably well with
experimental results when a around source explosion yield of
$283\pm38$ tons of TNT is utilized. This result, when
compared to the detonation of large hydrocarbon
fuel-drop-air clouds, suggests that only $14\pm2$ tons of
cyclohexane was involved in the explosion. Additionally the
time of the explosion determined from the model,
$15:52:08\pm6$, agrees, within the mutual uncertainty, with
that determined seismically, $15:52:15.5\pm2$ LIT. The
precision in the value of the yield and accuracy of the time
of the explosion validates the model used to describe the
propagation of acoustic waves by taking into account
expansion, absorption, and non-linear and inhomogeneous
effects in the atmosphere and ionosphere.}
}
@article{kressman1976,
author = {Kressman, R.I. and Piggott, W.R.},
title = {Combination of ionsonde and riometer data for absorption
measurements},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {107--109},
year = {1976},
volume = {38},
number = {1},
abstract = {A method is described for combining ionosonde and riometer
data which overcomes limitations in both techniques for the
measurement of normal absorption in the lower
ionosphere. The usefulness of these techniques is thereby
considerably increased.},
ukssdc_d = {},
uk_first = {}
}
@article{kumluca99:_tempor,
author = {Kumluca, A. and Tulunay, E. and Topalli, ?. and Tulunay,
Y.K.},
title = {Temporal and spatial forecasting of ionospheric critical
frequency using neural networks},
journal = {Radio Science},
pages = {1497--1506},
year = {1999},
volume = {34},
number = {6},
ukssdc_d = {}
}
@article{kutiev01,
author = {Kutiev, I. and Muhtarov, P.},
title = {Modeling of midlatitude F region response to geomagnetic
activity},
journal = {Journal of Geophysical Research},
pages = {15501--15509},
year = {2001},
month = {aug},
volume = {106},
number = {A8},
abstract = {An empirical model is developed to describe the variations
of midlatitude F region ionization along all longitudes
within the dip latitude band ($30^{\circ}-55^{\circ}$N),
induced by geomagnetic activity, by using the relative
deviations ($\Phi$) of the F region critical frequency
f$_{o}$F2 from its monthly median. The geomagnetic activity
is represented by the $K_{p}$ index. The main statistical
relationship between $\Phi$ and $K_{p}$ is obtained by using
11 years of data from 26 midlatitude ionosondes. The
statistical analysis reveals that the average dependence of
$\Phi$ on $K_{p}$ is quadratic, the average response of the
ionosphere to geomagnetic forcing is delayed with a time
constant $T$ of about 18 hours, and the instantaneous
distribution of $\Phi$ along local times can be assumed
sinusoidal. A continuity equation is written for $\Phi$ with
the "production term" being a function of Kp modulated by a
sinusoidal function of local time and the "loss" term
proportional to $\Phi$ with a loss coefficient
$\beta=1/T$. A new, modified function of geomagnetic
activity ($K_{f}$) is introduced, being proportional to
$\Phi$ averaged over all longitudes. The model is defined by
two standing sinusoidal waves with periods of 24 and 12
hours, rotating synchronously with the Sun, modulated by the
modified function $K_{f}$. The wave amplitudes and phases, as
well as their average offset, are obtained by fitting to the
data. A new error estimate called "prediction efficiency"
(Peff) is used, which assigns equal weights to the model
errors at all deviations of data from medians. The
prediction efficiency estimate gives a gain of accuracy of
29\%.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{kutiev2003,
author = {Kutiev, I. and Muhtarov, P.},
title = {Empirical modeling of global ionospheric f(o)F(2) response
to geomagnetic activity},
journal = {Journal of Geophysical Research},
year = {2003},
volume = {108},
number = {A1},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2001JA009134},
abstract = {The authors expand the previously developed midlatitude
model, providing the relative deviation of f$_{o}F2$ from
its monthly median value as a function of local time and Kp,
to the global scale. To achieve this, 55 ionosonde stations,
having at least 11 years of continuous data, have been
selected, and the model was applied to the data from each
station separately. Data from each station were grouped into
12-month bins, every bin containing all the available hourly
data within the respective month of the year. The model
considers the distribution of the relative deviation along
the local time at any fixed moment as composed of a diurnal
and a semidiurnal waves, expressed by five parameters: daily
mean (average offset), diurnal and semidiurnal amplitudes
and phases. The model expression is scaled by a modified
function of Kp, which reflects the delayed reaction of foF2
to Kp changes. The model parameters are determined by
fitting the model expression to the data in each bin. Their
distribution along the geomagnetic latitude is obtained in
three longitude sectors: North America-South America,
Europe-Africa, and East Asia-Australia. The seasonal
symmetry of model parameters in the Northern and Southern
Hemispheres, which is found to be acceptable, allows the use
of parameter values from both hemispheres in obtaining their
latitudinal profiles. In order to produce global
distribution of each of the model parameters, the respective
latitudinal profiles from the three sectors were averaged
and approximated by analytical expressions.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{lastovicka2005,
author = {Lastovicka, J.},
title = {On the role of solar and geomagnetic activity in long-term
trends in the atmosphere-ionosphere system},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2005},
volume = {67},
number = {1--2},
pages = {83--92},
ukssdc_d = {},
ukssdc_i = {},
abstract = {The long-term continuous increase of greenhouse gas
concentration in the atmosphere and other anthropogenic
influences represent serious threat for human
civilization. Therefore, it is necessary to determine the
long-term trends and changes in the atmosphere-ionosphere
system. The observed long-term trends in the 20th century
might be. however, influenced by contribution of Sun's
origin, and the process of determination of anthropoger c
trends from observational data may be "spoilt" by the
11-year solar cycle. The role of solar/geomagnetic activity
in long-term trends in various regions of the
atmosphere/ionosphere system is briefly reviewed for the
first time. The ways; of avoiding or at least diminishing
the effect of solar cycle on trend determination are
mentioned. As for the possible solar and geomagnetic
activity responsibility for part of the observed long-term
trends. the two main conclusions are as follows: (i) The
role of solar and geomagnetic activity in the observed
long-term trends decreases with decreasing altitude from the
F-region ionosphere down to the troposphere. (ii) In the
20th century the role of solar and geomagnetic activity in
the observed long-term trends/changes was decreasing from
its beginning towards its end.}
}
@article{lastovicka2003,
author = {Lastovicka, J. and Krizan, P. and Sauli, P. and Novotna, D.},
title = {Persistence of the planetary wave type oscillations in foF2
over Europe},
journal = {Annales Geophysicae},
year = {2003},
volume = {21},
number = {7},
pages = {1543--1552},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Planetary waves are oscillations of very predominantly
tropospheric origin with typical periods of about 2-30
days. Their dominant zonal wave numbers are 1, 2 and 3,
i.e. the waves are of large-scale (global) character. The
planetary wave type oscillations have been observed in the
lower and middle atmosphere but also in the ionosphere,
including the ionospheric F2-layer. Here, we deal only with
the oscillations analyzed for four European stations over a
solar cycle with the use of the Meyer and Morlet wavelet
transforms. Waves with periods near 5, 10 and 16 days are
studied. Only events with a duration of three wave-cycles
and more are considered. The 5-day period wave events
display a typical duration of 4 cycles, while 10- and 16-day
wave events are less persistent, with a typical duration of
about 3.5 cycles and 3 cycles, respectively. The persistence
pattern in terms of number of cycles and in terms of number
of days is different. In terms of number of cycles, the
typical persistence of oscillations decreases with
increasing period. On the other hand, in terms of number of
days the typical persistence evidently increases with
increasing period. The spectral distribution of event
duration is too broad to allow for a reasonable prediction
of event duration. Thus, the predictability of the planetary
wave type oscillations in foF2 seems to be very
questionable.}
}
@article{leitinger1985,
author = {Leitinger, R. and Dickinson, P.H.G. and Dumbs, A. and
Hartmann, G.K. and Hedberg, A. and Ranta, A.},
title = {The state of the F-region during the Energy Budget Campaign},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {49--60},
year = {1985},
volume = {47},
number = {1--3},
abstract = {The state of the F-region during the Energy Budget Campaign
(November/December 1980, Scandinavia) is analysed from
ionosonde and electron content data. Auxiliary data were
taken from other ground-based measurements and from in situ
measurements made during the Campaign. A description of the
overall state of the F-layer from mid-latitudes to high
latitudes is followed by a detailed analysis for the nights
November 10/11, November 15/16 and November 30/December 1,
which are of main interest for the Campaign. In higher
latitudes a distinct difference was found between the
geomagnetically 'quiet' period and the two 'disturbed'
periods. Under 'quiet' conditions a well defined trough was
observed moving equatorwards in the evening and back
polewards in the morning. Under 'disturbed' conditions the
latitude dependence of electron content changed
drastically. Near 60 deg of geomagnetic latitude a large
increase of ionization appeared which moved equatorwards
during the night. The magnitude of the enhancement depended
on the level of the local geomagnetic activity. The
enhancment effects are attributed to the precipitation of
soft electrons producing F-layer ionization in a region
confined in latitude but extended in longitude.},
ukssdc_d = {},
uk_other = {}
}
@article{li2003,
author = {Li, X.Y. and Yu, T.},
title = {Annual and semi-annual variations of the observed foF2 in a
high solar activity year},
journal = {Terrestrial Atmospheric and Oceanic Sciences},
year = {2003},
pages = {41--62},
volume = 14,
number = 1,
ukssdc_d = {},
ukssdc_i = {},
abstract = {By the Fourier series expanding method, the observed F2
layer critical frequencies (foF2) globally over 70 stations
in a high solar activity year of 1958, are used to analyze
the annual and semi-annual variations of foF2, and the world
wide distribution features of their amplitude and phase in
daytime and nighttime are studied in detail. The results for
foF2 annual and semi-annual variation are summarized as
follows. The midnight (2:00 LT) foF2 annual variations are
noticeable in both hemispheres at mid-high latitudes, and
their amplitudes are slightly larger in far pole regions
than in near pole regions. Generally, at most stations, the
midnight foF2 reach the maximum in summer, and no winter
anomaly can be discerned. While in daytime (14:00 LT), there
are pronounced annual variations with large amplitude in
both hemispheres at mid-high latitudes. After carefully
studying their phases, we find that these annual variations
usually peak in winter, which indicate all the variations
are classic winter anomaly. However, the winter anomaly is
very weak in the equatorial zone and not even perceivable in
South America. Moreover, the amplitude of daytime foF2
semi-annual variation is generally small in near pole
regions and large in far poles region of both
hemispheres. Compared with their annual component, the
semi-annual variations in the tropical region are
significant. Their phase distributions reveal that the
semi-annual variation usually peaks in March and April. In
order to explain the results mentioned above, we studied the
atomic molecular ratio [O/N$_{2}$] and confirmed that the
noon foF2 annual variations prevailing in mid-high latitudes
are caused largely by the annual variation of
[O/N$_{2}$]. As the noon foF2 semi-annual variations
pronounced in far pole regions, we should consider the
contribution of [O/N$_{2}$], the solar zenith angle, the
solar-driven low/mid-latitude thermospheric circulation and
the magnetospherically driven high-latitude
circulation. Moreover, we suggest that foF2 semi-annual
variations appearing in the equatorial zone are closely
related to other semi-annual variations in the upper
atmosphere, such as the semi-annual variation of
[O/N$_{2}$], the thermospheric circulation, the geomagnetic
activities and even the ionospheric electrical field.}
}
@article{liu1983,
author = {Liu, C. and Smith, P.A. and King, J.W.},
title = {A new solar index which leads to improved foF2 predictions
using the CCIR Atlas},
journal = {Telecommunications Journal},
pages = {408--414},
year = {1983},
volume = {50},
number = {VIII},
ukssdc_w = {},
ukssdc_d = {},
uk_other = {}
}
@article{liulb04,
author = {Liu, L. and Luan, X. and Wan, W. and Lei, J. and Ning, B.},
title = {Solar activity variations of equivalent winds derived from
global ionosonde data},
journal = {Journal of Geophysical Research},
year = {2004},
month = {dec},
volume = {109},
number = {A12},
url = {http://dx.doi.org/10.1029/2004JA010574},
abstract = {The equivalent winds at the F layer peak are derived from
global ionosonde data to investigate their solar activity
variations. With increasing solar activity, the derived
equivalent winds are found of nonlinearly decreased diurnal
amplitudes in all seasons at most stations. This implies
that the increase in ion drag more than compensates for
pressure gradients and thus restrains the diurnal amplitude
at high solar activity. The diurnal phase of the derived
equivalent winds generally shifts later at higher solar
activity. It is the first time to explicitly report this
striking feature that emerged at so many stations. Another
pronounced feature is that the diurnal phase has a
summer-winter difference. The diurnal phases at most
stations in the Northern Hemisphere are later in winter than
in summer at higher solar activity. Furthermore, a decrease
in the semidiurnal amplitudes of equivalent winds with
increasing solar activity is evident in winter over most
stations considered and in other seasons at stations with a
lower dip, but the decrease trend becomes weak in other
seasons at stations with a larger dip. However, complicated
dependences on solar activity can be found in the diurnal
mean and the semidiurnal phases of equivalent winds at
stations considered.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{lobzin2002,
author = {Lobzin, V.V. and Pavlov, A.V.},
title = {Solar zenith angle dependencies of F1-layer, NmF2 negative
disturbance, and G-condition occurrence probabilities},
journal = {Annales Geophysicae},
year = {2002},
volume = {20},
number = {11},
pages = {1821--1836},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Experimental data acquired by the Ionospheric Digital
Database of the National Geophysical Data Center, Boulder,
Colorado, from 1957 to 1990, are used to study the
dependence of the G condition, F1-layer, and NmF2 negative
disturbance occurrence probabilities on the solar zenith
angle during summer, winter, spring, and autumn months in
latitude range 1 (between $-10^{\circ}$ and $+10^{\circ}$ of
the geomagnetic latitude, $\Phi$), in latitude range 2
($10^{\circ} < |\Phi| \leq 30^{\circ}$), in latitude range 3
($30^{\circ} < |\phi| \leq 45^{\circ}, 30^{\circ} < |\Phi|
\leq 45^{\circ}$), in latitude range 4 ($45^{\circ} < |\phi|
\leq 60^{\circ}, 45^{\circ} < |\Phi| \leq 60^{\circ}$), and
in latitude range 5 ($60^{\circ} < |\Phi| \leq 90^{\circ}$),
where $\phi$ is the geographic latitude. Our calculations show
that the G condition is more likely to occur during the
first half of a day than during the second half of a day, at
all latitudes during all seasons for the same value of the
solar zenith angle. The F1-layer occurrence probability is
larger in the first half of a day in comparison with that in
the second half of a day for the same value of the solar
zenith angle in latitude range 1 for all seasons, while the
F1-layer occurrence probability is approximately the same
for the same solar zenith angle before and after noon in
latitude ranges 4 and 5. The F1-layer and G condition are
more commonly formed near midday than close to post sunrise
or pre-sunset. The chance that the daytime F1-layer and G
condition will be formed is greater in summer than in winter
at the given solar zenith angle in latitude ranges 2-5,
while the F1-layer occurrence probability is greater in
winter than in summer for any solar zenith angle in latitude
range 1. The calculated occurrence probability of the NmF2
weak negative disturbances reaches its maximum and minimum
values during daytime and night-time conditions,
respectively, and the average night-time value of this
probability is less than that by day for all seasons in all
studied latitude regions. It is shown that the NmF2 normal,
strong, and very strong negative disturbances are more
frequent on average at night than by day in latitude ranges
1 and 2 for all seasons, reaching their maximum and minimum
occurrence probability values at night and by day,
respectively. This conclusion is also correct for all other
studied latitude regions during winter months, except for
the NmF2 normal and strong negative disturbances in latitude
range 5. A difference in the dependence of the strong and
very strong NmF2 negative disturbance percentage occurrences
on the solar zenith angle is found between latitude ranges 1
and 2. Our results provide evidence that the daytime
dependence of the G condition occurrence probability on the
solar zenith angle is determined mainly by the dependence of
the F1-layer occurrence probability on the solar zenith
angle in the studied latitude regions for winter months, in
latitude range 2 for all seasons, and in latitude ranges 4
and 5 for spring, summer, and autumn months. The solar
zenith angle trend in the probability of the G condition
occurrence in latitude range 3 arises in the main from the
solar zenith angle trend in the F1-layer occurrence
probability. The solar zenith angle trend in the
probabilities of strong and very strong NmF2 negative
disturbances counteracts the identified solar zenith angle
trend in the probability of the G condition occurrence.}
}
@article{lockwood1989,
author = {Lockwood, M and Smith, Mark F.},
title = {Low-Altitude Signatures of the Cusp and Flux Transfer
Events},
journal = {Geophysical Research Letters},
pages = {879--882},
year = {1989},
month = aug,
volume = {16},
number = {8},
abstract = {The usual interpretation of a flux transfer event (FTE) at
magnetopause, in terms of time-dependent and possibly patchy
reconnection, demands that it generate an ionospheric
signature. Recent ground-based observations have revealed
that auroral transients in the cusp/cleft region have all
the characteristics required of FTE effects. However,
signatures in the major available dataset, namely that from
low-altitude polar-orbiting satellites, have not yet been
identified. In this paper, we consider a cusp pass of the
DE-2 spacecraft during strongly southward IMF. The particle
detectors show magnetosheath ion injection
signatures. However, the satellite motion and convection are
opposed, and we discuss how the observed falling energy
dispersion of the precipitating ions can have arisen from a
static, moving or growing source. The spatial scale of the
source is typical of an FTE. A simple model of the
ionospheric signature of an FTE reproduces the observed
electric and magnetic field perturbations. Precipitating
electrons of peak energy $\sim 100$ eV are found to lie on
the predicted boundary of the newly-opened tube, very
similar to those found on the edges of FTEs at the
magnetopause. The injected ions are within this boundary and
their dispersion is consistent with its growth as
reconnection proceeds. The reconnection potential and the
potential of the induced ionospheric motion are found to be
the same ($\simeq 25$ kV). The scanning imager on DE-1 shows
a localized transient auroral feature around DE-2 at this
time, similar to the recent optical/radar observations of
FTEs.},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood01,
author = {Lockwood, M.},
title = {The long-term drift in coronal source flux: origins and
implications},
journal = {AGU Spring Meeting Abstracts},
year = 2001,
month = may,
pages = {51-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001AGUSM..SH51A06L&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {By studying energy coupling between the solar wind and the
magnetosphere, Lockwood et al. (Nature, 399, 437, 1999)
obtained the highest reported correlation (0.97) between
interplanetary conditions and geomagnetic activity. By
inverting this theory and using the 27-day recurrence of
geomagnetic activity to eliminate the effect of fast flow
streams, these authors were able to compute the
interplanetary magnetic field from annual means of the aa
geomagnetic index. Because on annual time scales the IMF
obeys Parker spiral theory and using Ulysses results on the
3-dimensional structure of the heliosphere, these authors
were able to compute the total coronal source flux, the open
flux leaving the corona and entering the heliosphere. Test
with independent interplanetary data confirmed the validity
of the technique. The aa index is a homogeneous series
extending back to 1868 and the results showed that the
coronal source flux drifted upward throughout the last
century so that its solar cycle average was a factor of 2.4
larger by its end than in 1900. This rise is confirmed by
studies of isotopes deposited in ice sheets, tree rings and
meteorites by the action of cosmic ray bombardment, and
regression analysis with, for example $^{10}$Be abundances
in ice sheets reveals that the open solar flux fell to about
25 percent of present-day values by the end of the Maunder
minimum. Recent theoretic work by Solanki et al. (Nature,
408, 445, 2000) has explained this variation extremely well,
in terms of the length of the solar cycle and the rate at
which flux emerges through the photosphere. This therefore
relates the open flux variation to magnetic phenomena in the
photosphere (sunspots and faculae) that are known to
modulate the total solar irradiance.}
}
@article{lockwood01:_long_sun,
author = {Lockwood, M.},
title = {Long-term variations in the magnetic fields of the Sun and
the heliosphere: Their origin, effects, and implications},
journal = {Journal of Geophysical Research},
volume = 106,
number = {A8},
pages = {16021--16038},
year = 2001,
month = jan,
ukssdc_d = {},
uk_first = {},
url = {http://dx.doi.org/10.1029/2000JA000115},
abstract = {Recent studies of the variation of geomagnetic activity over
the past 140 years have quantified the "coronal source"
magnetic flux $F_{s}$ that leaves the solar atmosphere and
enters the heliosphere and have shown that it has risen, on
average, by an estimated 34\% since 1963 and by 140\% since
1900. This variation of open solar flux has been reproduced
by Solanki et al. [2000] using a model which demonstrates
how the open flux accumulates and decays, depending on the
rate of flux emergence in active regions and on the length
of the solar cycle. We here use a new technique to evaluate
solar cycle length and find that it does vary in association
with the rate of change of $F_{s}$ in the way predicted. The
long-term variation of the rate of flux emergence is found
to be very similar in form to that in $F_{s}$, which may
offer a potential explanation of why $F_{s}$ appears to be a
useful proxy for extrapolating solar total irradiance back
in time. We also find that most of the variation of cosmic
ray fluxes incident on Earth is explained by the strength of
the heliospheric field (quantified by $F_{s}$) and use
observations of the abundance of the isotope $^{10}$Be
(produced by cosmic rays and deposited in ice sheets) to
study the decrease in $F_{s}$ during the Maunder
minimum. The interior motions at the base of the convection
zone, where the solar dynamo is probably located, have
recently been revealed using the helioseismology technique
and found to exhibit a 1.3-year oscillation. This
periodicity is here reported in observations of the
interplanetary magnetic field and geomagnetic activity but
is only present after 1940. When present, it shows a strong
22-year variation, peaking near the maximum of even-numbered
sunspot cycles and showing minima at the peaks of
odd-numbered cycles. We discuss the implications of these
long-term solar and heliospheric variations for Earth's
environment.}
}
@article{lockwood01:_the_day,
author = {Lockwood, M.},
title = {The day the solar wind nearly died},
journal = {Nature},
year = 2001,
volume = 409,
month = feb,
ukssdc_d = {},
uk_first = {},
url = {http://www.nature.com/cgi-taf/DynaPage.taf%3Ffile%3D/nature/journal/v409/n6821/full/409677a0_fs.html%26content_filetype%3Dpdf}
}
@article{lockwood02,
author = {Lockwood, M.},
title = {An evaluation of the correlation between open solar flux and
total solar irradiance},
journal = {Astronomy & Astrophysics},
year = 2002,
volume = 382,
pages = {678--687},
ukssdc_d = {},
uk_first = {},
pdf = {http://www.edpsciences.org/articles/aa/pdf/2002/05/aa1957.pdf},
url = {http://www.edpsciences.org/papers/aa/full/2002/05/aa1957/aa1957.html},
abstract = {The correlation between the coronal source flux $F_{S}$ and
the total solar irradiance $I_{TS}$ is re-evaluated in the
light of an additional 5 years' data from the rising phase
of solar cycle 23 and also by using cosmic ray fluxes
detected at Earth. Tests on monthly averages show that the
correlation with $F_{S}$ deduced from the interplanetary
magnetic field (correlation coefficient, r = 0.62) is highly
significant (99.999\%), but that there is insufficient data
for the higher correlation with annual means ( r = 0.80) to
be considered significant. Anti-correlations between
$I_{TS}$ and cosmic ray fluxes are found in monthly data for
all stations and geomagnetic rigidity cut-offs ( r ranging
from -0.63 to -0.74) and these have significance levels
between 85\% and 98\%. In all cases, the fit is poorest for
the earliest data (i.e., prior to 1982). Excluding these
data improves the anticorrelation with cosmic rays to r =
-0.93 for one-year running means. Both the interplanetary
magnetic field data and the cosmic ray fluxes indicate that
the total solar irradiance lags behind the open solar flux
with a delay that is estimated to have an optimum value of
2.8 months (and is within the uncertainty range 0.8--8.0
months at the 90\% level).}
}
@inproceedings{lockwood02:_long,
author = {Lockwood, M.},
title = {Long-term variations in the open solar flux and possible
links to Earth's climate},
booktitle = {ESA SP-508: From Solar Min to Max: Half a Solar Cycle with
SOHO},
year = 2002,
month = jun,
pages = {507--522},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002soho...11..507L&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {Recent paleoclimate studies provide strong evidence for an
association between cosmogenic isotope production and
Earth's climate throughout the holocene. These isotopes are
generated by the bombardment of Earth's atmosphere by
galactic cosmic rays, the fluxes of which vary in
approximately inverse proportion to the total open magnetic
flux of the Sun. This paper discusses how results from the
Ulysses spacecraft allow us to quantify the open solar flux
from observations of near-Earth interplanetary space and to
study its long-term variations using the homogeneous record
of geomagnetic activity. A study of the results and of their
accuracy is presented. The two proposed mechanisms that
could lead to the open solar flux being a good proxy for
solar-induced climate change are discussed: the first is the
modulation of the production of some types of cloud by the
air ions produced by cosmic rays; the second is a variation
in the total or spectral solar irradiance, in association
with changes in the open flux. Some implications for our
understanding of anthropogenic climate change are
discussed.}
}
@article{lockwood02:_relat_earth,
author = {Lockwood, M.},
title = {Relationship between the near-Earth interplanetary field and
the coronal source flux: Dependence on timescale},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2002,
month = dec,
volume = 107,
number = {A12},
pages = {1-1},
doi = {10.1029/2001JA009062},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002JGRA.107l.SSH1L&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {The Ulysses spacecraft has shown that the radial component
of the heliospheric magnetic field is approximately
independent of latitude. This has allowed quantification of
the total open solar flux from near-Earth observations of
the interplanetary magnetic field. The open flux can also be
estimated from photospheric magnetograms by mapping the
fields up to the "coronal source surface" where the field is
assumed to be radial and which is usually assumed to be at a
heliocentric distance $r=2.5R_{S}$ (a mean solar radius,
$1R_{S}=6.96\times10^{8}$ m). These two classes of open flux
estimate will differ by the open flux that threads the
heliospheric current sheet(s) inside Earth's orbit at
$2.5R_{S}
@article{lockwood02:_solar_magnet_field_irrad_cosmic,
author = {Lockwood, M.},
title = {Solar Magnetic Fields, Irradiance, Cosmic Rays and Climate
Change},
journal = {EGS XXVII General Assembly, Nice, 21-26 April 2002, abstract
\#2921},
year = 2002,
volume = 27,
pages = {2921-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2002EGSGA..27.2921L&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {The abundances of cosmogenic isotopes are frequently used as
an indicator of solar variability in paleoclimate
studies. They reveal changes in the open magnetic flux of
the Sun; however, it is not clear what mechanism is at work
whereby this quantifies the effect of solar variations on
our climate. Studies of how geomagnetic activity is excited
by the solar wind flow have allowed quantification of this
open magnetic flux of the Sun, revealing it to have more
than doubled during the 20th century. The assumptions used
will be analysed in the light of the second perehelion pass
by the Ulysses spacecraft and shown to be valid, in that
they cause uncertainties of only a few percent. This flux
fills the heliosphere out to the termination shock and
shields Earth from galactic cosmic rays (GCRs) and, indeed,
a strong anti-correlation between GCR fluxes and the open
solar flux estimates is found. This open flux is also found
to have a surprisingly strong correlation with the total
solar irradiance (TSI) variation caused by magnetic flux
threading the solar photosphere. This correlation is shown
to hold in the latest TSI data from the SoHO spacecraft. The
correlations of various indictors of terrestrial climate
with GCRs and TSI are very similar in their strength and
significance, making distinction between potential TSI and
GCR effects difficult to achieve.}
}
@article{lockwood03:_twent,
author = {Lockwood, M.},
title = {Twenty-three cycles of changing open solar magnetic flux},
journal = {Journal of Geophysical Research},
year = 2003,
volume = 108,
number = {A3},
pages = 1128,
url = {http://dx.doi.org/10.1029/2002JA009431},
ukssdc_d = {},
uk_first = {},
abtsract = {This paper presents a comparison of various estimates of the
open solar flux, deduced from measurements of the
interplanetary magnetic field, from the aa geomagnetic index
and from photospheric magnetic field observations. The first
two of these estimates are made using the Ulysses discovery
that the radial heliospheric field is approximately
independent of heliographic latitude, the third makes use of
the potential-field source surface method to map the total
flux through the photosphere to the open flux at the top of
the corona. The uncertainties associated with using the
Ulysses result are 5\%, but the effects of the assumptions
of the potential field source surface method are harder to
evaluate. Nevertheless, the three methods give similar
results for the last three solar cycles when the data sets
overlap. In 11-year running means, all three methods reveal
that 1987 marked a significant peak in the long-term
variation of the open solar flux. This peak is close to the
solar minimum between sunspot cycles 21 and 22, and
consequently the mean open flux (averaged from minimum to
minimum) is similar for these two cycles. However, this
similarity between cycles 21 and 22 in no way implies that
the open flux is constant. The long-term variation shows
that these cycles are fundamentally different in that the
average open flux was rising during cycle 21 (from
consistently lower values in cycle 20 and toward the peak in
1987) but was falling during cycle 22 (toward consistently
lower values in cycle 23). The estimates from the
geomagnetic aa index are unique as they extend from 1842
onwards (using the Helsinki extension). This variation gives
strong anticorrelations, with very high statistical
significance levels, with cosmic ray fluxes and with the
abundances of the cosmogenic isotopes that they
produce. Thus observations of photospheric magnetic fields,
of cosmic ray fluxes, and of cosmogenic isotope abundances
all support the long-term drifts in open solar flux reported
by Lockwood et al. [1999a , 1999b].}
}
@inproceedings{lockwood1995,
key = {RAL-P-95-002},
author = {Lockwood, M.},
editor = {Alcayd{\'{e}}, D.},
title = {Solar Wind - Magnetospheric Coupling},
booktitle = {Proceedings of the EISCAT International School},
organization = {EISCAT},
year = {1995},
month = {September},
publisher = {CLRC},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood95:_large,
author = {Lockwood, M.},
title = {Large-scale fields and flows in the magnetosphere-ionosphere
system},
journal = {Surveys in Geophysics (Historical Archive)},
year = 1995,
volume = 16,
number = 3,
pages = {389--441},
ukssdc_d = {},
uk_first = {},
abstract = {Advances in our understanding of the large-scale electric
and magnetic fields in the coupled magnetosphere-ionosphere
system are reviewed. The literature appearing in the period
January 1991--June 1993 is sorted into 8 general areas of
study. The phenomenon of substorms receives the most
attention in this literature, with the location of onset
being the single most discussed issue. However, if the
magnetic topology in substorm phases was widely debated,
less attention was paid to the relationship of convection to
the substorm cycle. A significantly new consensus view of
substorm expansion and recovery phases emerged, which was
termed the "Kiruna Conjecture" after the conference at which
it gained widespread acceptance. The second largest area of
interest was dayside transient events, both near the
magnetopause and the ionosphere. It became apparent that
these phenomena include at least two classes of events,
probably due to transient reconnection bursts and sudden
solar wind dynamic pressure changes. The contribution of
both types of event to convection is controversial. The
realisation that induction effects decouple electric fields
in the magnetosphere and ionosphere, on time scales shorter
than several substorm cycles, calls for broadening of the
range of measurement techniques in both the ionosphere and
at the magnetopause. Several new techniques were introduced
including ionospheric observations which yield reconnection
rate as a function of time. The magnetospheric and
ionospheric behaviour due to various quasi-steady
interplanetary conditions was studied using magnetic cloud
events. For northward IMF conditions, reverse convection in
the polar cap was found to be predominantly a summer
hemisphere phenomenon and even for extremely rare prolonged
southward IMF conditions, the magnetosphere was observed to
oscillate through various substorm cycles rather than
forming a steady-state convection bay.}
}
@article{lockwood1988,
author = {Lockwood, M. and Cowley, S.W.H.},
title = {Observations at the Magnetopause and in the Auroral
Ionosphere of Momentum Transfer from the Solar Wind},
journal = {Advances in Space Research},
pages = {(9)281--(9)299},
year = {1988},
volume = {8},
number = {9--10},
abstract = {Recent radar studies of field-perpendicular flows in the
auroral ionosphere, in conjunction with observations of the
interplanetary medium immediately upstream of the Earth's
bow shock, have revealed direct control of dayside
convection by the Bz component of the interplanetary
magnetic field (IMF). The ionospheric flows begin to respond
to both northward and southward turnings of the IMF
impinging upon the magnetopause after a delay of only a few
minutes in the early afternoon sector, rising to about 15
minutes nearer dawn and dusk. In both the polar cap and the
auroral oval, the subsequent rise and decay times are of
order 5-10 minutes. We conclude there is very little
convection "flywheel" effect in the dayside polar ionosphere
and that only newly-opened flux tubes impart significant
momentum to the ionosphere, in a relatively narrow region
immediately poleward of the cusp. These findings concerning
the effects of quasi-steady reconnection have important
implications for any ionospheric signatures of transient
reconnection which should be considerably shorter-lived than
thought hitherto. In order to demonstrate the difficulty of
uniquely identifying a Flux Transfer Event (FTE) in
ground-based magnetometer data, we present observations of
an impulsive signature, identical with that expected for an
FTE if data from only one station is studied, following an
observed magnetopause compression when the IMF was purely
northward. We also report new radar observations of a
viscous-like interaction, consistent with an origin on the
flanks of the magnetotail and contributing an estimated
15-30kV to the total cross-cap potential during quiet
periods.},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood1990,
author = {Lockwood, M. and Cowley, S.W.H. and Sandholt, P.E.},
title = {Transient Reconnection - Search for Ionospheric Signatures},
journal = {EOS},
pages = {709,719--720},
year = {1990},
month = may,
volume = {71},
number = {20},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood11993,
author = {Lockwood, M. and Denig, W.F. and Farmer, A.D. and Davda,
V.N. and Cowley, S.W.H. and L{\"{u}}hr, H.},
title = {Ionospheric signatures of pulsed reconnection at the Earth's
magnetopause},
journal = {Nature},
pages = {424--427},
year = {1993},
month = feb,
volume = {361},
ukssdc_d = {},
abstract = {The plasma precipitating into the Earth's dayside auroral
atmosphere has characteristics which show that it originates
from the shocked solar-wind plasma of the magnetosheath. The
particles of the magnetosheath plasma precipitate down a
funnel-shaped region (cusp) of open field lines resulting
from reconnection of the geomagnetic field with the
interplanetary magnetic field. Although the cusp has long
been considered a well defined spatial structure maintained
by continuous reconnection, it has recently been suggested
that reconnection instead may take place in a series of
discontinuous events; this is the 'pulsating cusp
model'. Here we present coordinated radar and satellite
observations of a series of discrete, poleward-moving plasma
structures that are consistent with the pulsating-cusp
model.},
uk_first = {}
}
@article{lockwood04:_open_earth,
author = {Lockwood, M. and Forsyth, R.B. and Balogh, A. and McComas,
D.J.},
title = {Open solar flux estimates from near-Earth measurements of
the interplanetary magnetic field: comparison of the first
two perihelion passes of the Ulysses spacecraft},
journal = {Annales Geophysicae},
year = 2004,
volume = 22,
number = 4,
pages = {1395--1405},
abstract = {Results from all phases of the orbits of the Ulysses
spacecraft have shown that the magnitude of the radial
component of the heliospheric field is approximately
independent of heliographic latitude. This result allows the
use of near-Earth observations to compute the total open
flux of the Sun. For example, using satellite observations
of the interplanetar), magnetic field, the average open
solar flux was shown to have risen by 29\% between 1963 and
1987 and using the aa geomagnetic index it was found to have
doubled during the 20th century. It is therefore important
to assess fully the accuracy of the result and to check that
it applies to all phases of the solar cycle. The first
perihelion pass of the Ulysses spacecraft was close to
sunspot minimum, and recent data from the second perihelion
pass show that the result also holds at solar maximum. The
hi-h level of correlation between the open flux derived from
the various methods strongly supports the Ulysses discovery
that the radial field component is independent of
latitude. We show here that the errors introduced into open
solar flux estimates by assuming that the heliospheric
field's radial component is independent of latitude are
similar for the two passes and are of order 25\% for daily
values, failing to 5\% for averaging timescales of 27 days
or greater. We compare here the results of four methods for
estimating the open solar flu), with results from the first
and second perehelion passes by Ulysses. We find that the
errors are lowest (1-5\% for averages over the entire
perehelion passes lasting near 320 days), for near-Earth
methods, based on either interplanetary magnetic field
observations or the aa geomagnetic activity index. The
corresponding errors for the Solanki et al. (2000) model are
of the order of 9-15\% and for the PFSS method, based on
solar magnetograms, are of the order of 13-47\%. The model
of Solanki et al. is based on the continuity equation of
open flux, and uses the sunspot number to quantify the rate
of open flux emergence. It predicts that the average open
solar flux has been decreasing since 1987, as is observed in
the variation of all the estimates of the open flux. This
decline combines with the solar cycle variation to produce
an open flux during the second (sunspot maximum) perihelion
pass of Ulysses which is only slightly larger than that
during the first (sunspot minimum) perihelion pass.},
ukssdc_d = {},
uk_first = {}
}
@inproceedings{lockwood01:_long,
author = {Lockwood, M. and Foster, S.},
title = {Long-term variations in the magnetic fields of the sun and
possible implications for terrestrial climate},
booktitle = {SOLSPA Euroconference},
organization = {ESA},
year = {2001},
series = {ESA-SP??},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood03:_are,
author = {Lockwood, M. and Foster, S.S.},
title = {Are there links between long-term changes in open solar
flux, the distribution of emerged flux, cosmogenic isotopes
and the total solar irradiance?},
journal = {AGU Fall Meeting Abstracts},
year = 2003,
month = dec,
pages = {C3+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003AGUFMSH31C..03L&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {Recent reconstructions of variations in the total solar
irradiance (TSI) over the last 300 years are similar in form
to the variations of cosmogenic isotope abundances and the
inferred variation of the open solar flux over the same
interval. These reconstructions show a century-scale drift
in TSI which is comparable in magnitude to the amplitude of
recent solar cycle changes, namely of order $1Wm^{-2}$. In
addition, strong links between paleoclimate records and
cosmogenic isotopes have been found. These results also
suggest a link between open solar flux and total solar
irradiance. Modelling of the evolution of emerged flux by
Wang et al. (2002) reproduces the inferred large changes (by
a factor of order 2) in the open solar flux on century
timescales, explaining the changes in cosmic ray fluxes and
hence cosmogenic isotope abundance: however, this modelling
also suggests that this is not associated with significant
change in the photospheric magnetic flux, which modulates
TSI on 11-year timescales. Thus the changes in the open flux
and cosmogenic isotopes do not appear to be linked to the
100-year drift in TSI. The long-term variation in open flux
has been shown to be associated with changes in the
heliographic latitude of active regions and we show that the
contribution of active region faculae to the TSI has changed
by $0.2Wm^{-2}$ in the past 100 years because of the
directional characteristics of the excess radiation from
faculae. This suggests that small flux tubes of the
"extended solar cycle", and any long-term change in their
latitudes, could also have made a significant contribution
to the long-term drift in TSI.}
}
@article{lockwood07:_recen,
author = {Lockwood, M. and Fr\"ohlich, C.},
title = {Recent oppositely directed trends in solar climate forcings
and the global mean surface air temperature},
journal = {Proc. R. Soc. A},
year = 2007,
volume = 463,
number = 2086,
pages = {2447--2460},
abstract = {There is considerable evidence for solar influence on the
Earth's pre-industrial climate and the Sun may well have
been a factor in post-industrial climate change in the first
half of the last century. Here we show that over the past 20
years, all the trends in the Sun that could have had an
influence on the Earth's climate have been in the opposite
direction to that required to explain the observed rise in
global mean temperatures.},
url = {http://dx.doi.org/10.1098/rspa.2007.1880/},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood89:_recen,
author = {Lockwood, M. and Freeman, M.P.},
title = {Recent ionospheric observations relating to
solar-wind-magnetosphere coupling},
journal = {Phil. Trans. R. Soc. Lond.},
pages = {93--105},
year = {1989},
volume = {A},
number = {328},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood98,
author = {Lockwood, M. and Hapgood, M.},
title = {On the cause of a magnetospheric flux transfer event},
journal = {Journal of Geophysical Research},
pages = {26453--26478},
year = {1998},
month = {nov},
volume = {103},
number = {A11},
abstract = {We present a detailed investigation of a magnetospheric flux
transfer event (FTE) seen by the Active Magnetospheric
Tracer Explorer (AMPTE) UKS and IRM satellites around 1046
UT on October 28, 1984. This event has been discussed many
times previously in the literature and has been cited as
support for a variety of theories of FTE formation. We make
use of a model developed to reproduce ion precipitations
seen in the cusp ionosphere. The analysis confirms that the
FTE is well explained as a brief excursion into an open
low-latitude boundary layer (LLBL), as predicted by two
theories of magnetospheric FTEs, namely, that they are
bulges in the open LLBL due to reconnection rate
enhancements or that they are indentations of the
magnetopause by magnetosheath pressure increases (but in the
presence of ongoing steady reconnection). The indentation of
the inner edge of the open LLBL that these two models seek
to explain is found to be shallow for this event. The ion
model reproduces the continuous evolution of the ion
distribution function between the sheath-like population at
the event center and the surrounding magnetospheric
populations; it also provides an explanation of the
high-pressure core of the event as comprising field lines
that were reconnected considerably earlier than those that
are draped over it to give the event boundary layer. The
magnetopause transition parameter is used to isolate a field
rotation on the boundaries of the core, which is subjected
to the tangential stress balance test. The test identifies
this to be a convecting structure, which is neither a
rotational discontinuity (RD) nor a contact discontinuity,
but could possibly be a slow shock. In addition, evidence
for ion reflection off a weak RD on the magnetospheric side
of this structure is found. The event structure is
consistent in many ways with features predicted for the open
LLBL by analytic MHD theories and by MHD and hybrid
simulations. The de Hoffman-Teller velocity of the structure
is significantly different from that of the magnetosheath
flow, indicating that it is not an indentation caused by a
high-pressure pulse in the sheath but is consistent with the
motion of newly opened field lines (different from the
sheath flow because of the magnetic tension force) deduced
from the best fit to the ion data. However, we cannot here
rule out the possibility that the sheath flow pattern has
changed in the long interval between the two satellites
observing the FTE and subsequently emerging into the
magnetosheath; thus this test is not conclusive in this
particular case. Analysis of the fitted elapsed time since
reconnection shows that the core of the event was
reconnected in one pulse and the event boundary layer was
reconnected in a subsequent pulse. Between these two pulses
is a period of very low (but nonzero) reconnection rate,
which lasts about 14 mins. Thus the analysis supports, but
does not definitively verify, the concept that the FTE is a
partial passage into an open LLBL caused by a traveling
bulge in that layer produced by a pulse in reconnection
rate.},
ukssdc_d = {},
uk_first = {}
}
@article{2006JGRA..11102306L,
author = {Lockwood, M. and Lanchester, B.S. and Morley, S.K. and
Throp, K. and Milan, S.E. and Lester, M. and Frey, H.U. },
title = {{Modeling the observed proton aurora and ionospheric
convection responses to changes in the IMF clock angle:
2. Persistence of ionospheric convection}},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2006,
month = feb,
volume = 111,
number = {A10},
pages = {2306-+},
doi = {10.1029/2003JA010307},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRA..11102306L},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {We apply a numerical model of time-dependent ionospheric
convection to two directly driven reconnection pulses during
a 15-min interval of southward IMF on 26 November 2000. The
model requires an input magnetopause reconnection rate
variation, which is here derived from the observed variation
in the upstream IMF clock angle, $\theta$. The reconnection
rate is mapped to an ionospheric merging gap, the MLT extent
of which is inferred from the Doppler-shifted Lyman-$\alpha$
emission on newly opened field lines, as observed by the FUV
instrument on the IMAGE spacecraft. The model is used to
reproduce a variety of features observed during this event:
SuperDARN observations of the ionospheric convection pattern
and transpolar voltage; FUV observations of the growth of
patches of newly opened flux; FUV and in situ observations
of the location of the Open-Closed field line Boundary (OCB)
and a cusp ion step. We adopt a clock angle dependence of
the magnetopause reconnection electric field, mapped to the
ionosphere, of the form $E_{no}\mathrm{sin}^{4}(\theta/2)$ and
estimate the peak value, $E_{no}$, by matching observed and
modeled variations of both the latitude, $\Lambda_{OCB}$, of
the dayside OCB (as inferred from the equatorward edge of
cusp proton emissions seen by FUV) and the transpolar
voltage $\Phi_{PC}$ (as derived using the mapped potential
technique from SuperDARN HF radar data). This analysis also
yields the time constant $\tau_{OCB}$ with which the
open-closed boundary relaxes back toward its equilibrium
configuration. For the case studied here, we find $\tau_{OCB} =
9.7 \pm 1.3$ min, consistent with previous inferences
from the observed response of ionospheric flow to southward
turnings of the IMF. The analysis confirms quantitatively
the concepts of ionospheric flow excitation on which the
model is based and explains some otherwise anomalous
features of the cusp precipitation morphology. },
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{lockwood03:_IMFcont,
author = {Lockwood, M. and Lanchester, H. U. and Frey, K. and Throp,
K. and Morely, S. K. and Milan, S. E and Lester, M.},
title = {IMF control of cusp proton emission intensity and dayside
convection: implications for component and anti-parallel
reconnection},
journal = {Annales Geophysicae},
pages = {955-982},
year = {2003},
volume = {21},
number = {4},
abstract = {We study a brightening of the Lyman-a emission in the cusp
which occurred in response to a short-lived south-ward
turning of the interplanetary magnetic field (IMF) during a
period of strongly enhanced solar wind plasma
concentration. The cusp proton emission is detected using
the SI-12 channel of the FUV imager on the IMAGE
spacecraft. Analysis of the IMF observations recorded by the
ACE and Wind spacecraft reveals that the assumption of a
constant propagation lag from the upstream spacecraft to the
Earth is not adequate for these high time-resolution
studies. The variations of the southward IMF component
observed by ACE and Wind allow for the calculation of the
ACE-to-Earth lag as a function of time. Application of the
derived propagation delays reveals that the intensity of the
cusp emission varied systematically with the IMF clock
angle, the relationship being particularly striking when the
intensity is normalised to allow for the variation in the
upstream solar wind proton concentration. The latitude of
the cusp migrated equatorward while the lagged IMF pointed
southward, confirming the lag calculation and indicating
ongoing magnetopause reconnection. Dayside convection, as
monitored by the SuperDARN network of radars, responded
rapidly to the IMF changes but lagged behind the cusp proton
emission response: this is shown to be as predicted by the
model of flow excitation by Cowley and Lockwood (1992). We
use the numerical cusp ion precipitation model of Lockwood
and Davis (1996), along with modelled Lyman-a emission
efficiency and the SI-12 instrument response, to investigate
the effect of the sheath field clock angle on the
acceleration of ions on crossing the dayside
magnetopause. This modelling reveals that the emission
commences on each reconnected field line 2-2.5 min after it
is opened and peaks 3-5 min after it is opened. We discuss
how comparison of the Lyman-a intensities with oxygen
emissions observed simultaneously by the SI-13 channel of
the FUV instrument offers an opportunity to test whether or
not the clock angle dependence is consistent with the
"component" or the "anti-parallel" reconnection hypothesis.},
ukssdc_d = {},
uk_first = {}
}
@article{lockwood01:_cusp,
author = {Lockwood, M. and Milan, S.~E. and Onsager, T. and
Perry, C.~H. and Scudder, J.~A. and Russell, C.~T. and
Brittnacher, M.},
title = {Cusp ion steps, field-aligned currents and poleward moving
auroral forms},
journal = {Journal of Geophysical Research},
year = 2001,
month = dec,
volume = 106,
number = {A12},
pages = {29555--29570},
url = {http://dx.doi.org/10.1029/2000JA900175},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001JGR...10629555L&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_first = {},
abstract = {We predict the field-aligned currents around cusp ion steps
produced by pulsed reconnection between the geomagnetic
field and an interplanetary magnetic field (IMF) with a
$B_{Y}$ component that is large in magnitude. For $B_{Y}>0$,
patches of newly opened flux move westward and eastward in
the Northern and Southern Hemispheres, respectively, under
the influence of the magnetic curvature force. These flow
directions are reversed for $B_{Y}<0$. The speed of this
longitudinal motion initially grows with elapsed time since
reconnection, but then decays as the newly opened field
lines straighten. We predict sheets of field-aligned current
on the boundaries between the patches produced by successive
reconnection pulses, associated with the difference in the
speeds of their longitudinal motion. For low elapsed times
since reconnection, near the equatorward edge of the cusp
region where the field lines are accelerating, the
field-aligned current sheets will be downward or upward in
both hemispheres for positive or negative IMF $B_{Y}$,
respectively. At larger elapsed times since reconnection, as
events slow and evolve from the cusp into the mantle region,
these field-aligned current directions will be
reversed. Observations by the Polar spacecraft on August 26,
1998, show the predicted upward current sheets at steps seen
in the mantle region for IMF $B_{Y}>0$. Mapped into the
ionosphere, the steps coincide with poleward moving events
seen by the CUTLASS HF radar. The mapped location of the
largest step also coincides with a poleward moving arc seen
by the UVI imager on Polar. We show that the arc is
consistent with a region of upward field-aligned current
that has become unstable, such that a potential drop of
about 1 kV formed below the spacecraft. The importance of
these observations is that they confirm that the poleward
moving events, as seen by the HF radar and the UV imager,
are due to pulsed magnetopause reconnection. Milan et
al. [2000] noted that the great longitudinal extent of these
events means that the required reconnection pulses would
have contributed almost all the voltage placed across the
magnetosphere at this time. The observations also show that
auroral arcs can form on open field lines in response to the
pulsed application of voltage at the magnetopause.}
}
@article{2006JGRA..11109109L,
author = {Lockwood, M. and Rouillard, A.P. and Finch, I. and Stamper,
R.},
title = {{Comment on ``The IDV index: Its derivation and use in
inferring long-term variations of the interplanetary
magnetic field strength'' by Leif Svalgaard and Edward
W. Cliver}},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2006,
month = sep,
volume = 111,
number = {A10},
pages = {9109-+},
doi = {10.1029/2006JA011640},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRA..11109109L},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {},
ukssdc_w = {}
}
@article{lockwood1999,
author = {Lockwood, M. and Stamper, R.},
title = {Long-term drift of the coronal source magnetic flux and the
total solar irradiance},
journal = {Geophysical Research Letters},
pages = {2461-2464},
year = 1999,
month = {august},
volume = 26,
number = 16,
ukssdc_w = {},
ukssdc_d = {},
uk_first = {},
abstract = {We test the method of Lockwood et al. [1999] for deriving
the coronal source flux from the geomagnetic aa index and
show it to be accurate to within 12\% for annual means and
4.5\% for averages over a sunspot cycle. Using data from
four solar constant monitors during 1981--1995, we find a
linear relationship between this magnetic flux and the total
solar irradiance. From this correlation, we show that the
131\% rise in the mean coronal source field over the
interval 1901--1995 corresponds to a rise in the average
total solar irradiance of $\Delta I = 1.65 \pm 0.23
Wm^{-2}$.},
url = {grlcover.html}
}
@article{lockwood1999:_doubling_coronal_mag_field,
author = {Lockwood, M. and Stamper, R. and Wild, M.},
title = {A Doubling of the Sun's Coronal Magnetic Field during the
Last 100 Years},
journal = {Nature},
volume = 399,
pages = {437--439},
year = 1999,
month = {june},
abstract = {The solar wind is an extended ionized gas of very high
electrical conductivity, and therefore drags some magnetic
flux out of the Sun to fill the heliosphere with a weak
interplanetary magnetic field,. Magnetic reconnection -- the
merging of oppositely directed magnetic fields -- between
the interplanetary field and the Earth's magnetic field
allows energy from the solar wind to enter the near-Earth
environment. The Sun's properties, such as its luminosity,
are related to its magnetic field, although the connections
are still not well understood,. Moreover, changes in the
heliospheric magnetic field have been linked with changes in
total cloud cover over the Earth, which may influence global
climate. Here we show that measurements of the near-Earth
interplanetary magnetic field reveal that the total magnetic
flux leaving the Sun has risen by a factor of 1.4 since
1964: surrogate measurements of the interplanetary magnetic
field indicate that the increase since 1901 has been by a
factor of 2.3. This increase may be related to chaotic
changes in the dynamo that generates the solar magnetic
field. We do not yet know quantitatively how such changes
will influence the global environment.},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {},
pdf = {http://www.nature.com/nature/journal/v399/n6735/pdf/399437a0.pdf},
url = {http://www.nature.com/nature/journal/v399/n6735/abs/399437a0.html},
doi = {10.1038/20867}
}
@techreport{lockwood95:_groun_based_measur_suppor_clust,
author = {Lockwood, M. and Stamper, R. and Wild, M.N. and Opgenoorth,
H.J.},
title = {Ground-Based Measurements in Support of CLUSTER: An On-Line
Planning Procedure},
institution = {DRAL},
year = {1995},
month = feb,
number = {RAL-95-018},
ukssdc_d = {},
ukssdc_w = {},
uk_first = {}
}
@article{lockwood99:_onset_expan_enhan_ionos_convec,
author = {Lockwood, M. and Wild, M.N. and Cowley, S.W.H.},
title = {The Onset and Expansion of Enhanced Ionospheric Convection
Following a Southward Turning of the IMF},
journal = {Journal of Geophysical Research},
year = {1999},
note = {submitted},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@inproceedings{lockwood99:_predic,
author = {Lockwood, M. and Wild, M.N. and Stamper, R. and Grande, M.},
title = {Predicting solar disturbance effects on navigation systems},
booktitle = {Journal of Navigation},
pages = {203--216},
year = {1999},
volume = {52},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{ma2003,
author = {Ma, R.P. and Xu, H.Y. and Liao, H.},
title = {The features and a possible mechanism of semiannual
variation in the peak electron density of the low latitude
F2 layer},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
volume = {65},
number = {1},
pages = {47--57},
year = {2003},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Ionospheric data observed in 30 stations located in 3
longitude sectors (East Asia/Australia Sector, Europe/Africa
Sector and America/East Pacific Ocean Sector) during
1974-1986 are used to analyse the characteristics of
semiannual variation in the peak electron density of F2
layer (NmF2). The results indicate that the semiannual
variation of NmF2 mainly presents in daytime. In nighttime,
except in the region of geomagnetic equator between the two
crests of ionospheric equatorial anomaly, NmF2 has no
obvious semiannual variation. In the high latitude region,
only in solar maxima years and in daytime, there are obvious
semiannual variations of NmF2. The amplitude distribution of
the semiannual variation of daytime NmF2 with latitude has a
"double-humped structure", which is very similar to the
ionospheric equatorial anomaly. There is asymmetry between
the Southern and the Northern Hemispheres of the profile of
the amplitude of semiannual variation of NmF2 and
longitudinal difference. A new possible mechanism of
semiannual variation of NmF2 is put forward in this
paper. The semiannual variation of the diurnal tide in the
lower thermosphere induces the semiannual variation of the
amplitude of the equatorial electrojet. This causes the
semiannual variation of the amplitude of ionospheric
equatorial anomaly through fountain effect. This process
induces the semiannual variation of the low latitude NmF2.}
}
@article{mackay02:_evolut_open_magnet_fluxII,
author = {Mackay, D.H. and Lockwood M.},
title = {The Evolution of the Sun's Open Magnetic Flux -- II. Full
Solar Cycle Simulations},
journal = {Solar Physics},
year = 2002,
volume = 209,
number = 2,
pages = {287--309},
month = oct,
ukssdc_d = {},
uk_first = {},
abstract = {In this paper the origin and evolution of the Sun's open
magnetic flux is considered by conducting magnetic flux
transport simulations over many solar cycles. The
simulations include the effects of differential rotation,
meridional flow and supergranular diffusion on the radial
magnetic field at the surface of the Sun as new magnetic
bipoles emerge and are transported poleward. In each cycle
the emergence of roughly 2100 bipoles is considered. The net
open flux produced by the surface distribution is calculated
by constructing potential coronal fields with a source
surface from the surface distribution at regular
intervals. In the simulations the net open magnetic flux
closely follows the total dipole component at the source
surface and evolves independently from the surface flux. The
behaviour of the open flux is highly dependent on meridional
flow and many observed features are reproduced by the
model. However, when meridional flow is present at observed
values the maximum value of the open flux occurs at cycle
minimum when the polar caps it helps produce are the
strongest. This is inconsistent with observations by
Lockwood, Stamper and Wild (1999) and Wang, Sheeley, and
Lean (2000) who find the open flux peaking 1--2 years after
cycle maximum. Only in unrealistic simulations where
meridional flow is much smaller than diffusion does a
maximum in open flux consistent with observations occur. It
is therefore deduced that there is no realistic parameter
range of the flux transport variables that can produce the
correct magnitude variation in open flux under the present
approximations. As a result the present standard model does
not contain the correct physics to describe the evolution of
the Sun's open magnetic flux over an entire solar
cycle. Future possible improvements in modeling are
suggested.}
}
@article{mackay02:_evolut_open_magnet_fluxI,
author = {Mackay, D.H. and Priest, E.R. and Lockwood, M.},
title = {The Evolution of the Sun's Open Magnetic Flux -- I. A Single
Bipole},
journal = {Solar Physics},
year = 2002,
volume = 207,
number = 2,
pages = {291--308},
month = jun,
ukssdc_d = {},
uk_first = {},
abstract = {In this paper the origin and evolution of the Sun's open
magnetic flux are considered for single magnetic bipoles as
they are transported across the Sun. The effects of magnetic
flux transport on the radial field at the surface of the Sun
are modeled numerically by developing earlier work by Wang,
Sheeley, and Lean (2000). The paper considers how the
initial tilt of the bipole axis ($\alpha$) and its latitude
of emergence affect the variation and magnitude of the
surface and open magnetic flux. The amount of open magnetic
flux is estimated by constructing potential coronal
fields. It is found that the open flux may evolve
independently from the surface field for certain ranges of
the tilt angle. For a given tilt angle, the lower the
latitude of emergence, the higher the magnitude of the
surface and open flux at the end of the simulation. In
addition, three types of behavior are found for the open
flux depending on the initial tilt angle of the bipole
axis. When the tilt is such that $\alpha\geq2^{\circ}$ the open
flux is independent of the surface flux and initially
increases before decaying away. In contrast, for tilt angles
in the range $-16^{\circ}<\alpha<2^{\circ}$ the open flux follows
the surface flux and continually decays. Finally, for
$\alpha\leq-16^{\circ}$ the open flux first decays and then
increases in magnitude towards a second maximum before
decaying away. This behavior of the open flux can be
explained in terms of two competing effects produced by
differential rotation. Firstly, differential rotation may
increase or decrease the open flux by rotating the centers
of each polarity of the bipole at different rates when the
axis has tilt. Secondly, it decreases the open flux by
increasing the length of the polarity inversion line where
flux cancellation occurs. The results suggest that, in order
to reproduce a realistic model of the Sun's open magnetic
flux over a solar cycle, it is important to have accurate
input data on the latitude of emergence of bipoles along
with the variation of their tilt angles as the cycle
progresses.}
}
@article{mansilla2004:_mid_latitude,
author = {Mansilla, G.A.},
title = {Mid-latitude ionospheric effects of a great geomagnetic
storm},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2004},
volume = {66},
number = {12},
pages = {1085--1091},
ukssdc_d = {},
ukssdc_i = {},
abstract = {On March 13, 1989 magnetic storm effects on the mid- and
low-latitude ionosphere were investigated. For this, peak
electron density of 172-layer (NmF2) data from four chains
of ionospheric stations located in the geographic longitude
ranges $10^{\circ}$W-$15^{\circ}$E,
$55^{\circ}$E-$85^{\circ}$E, $135^{\circ}$E-$155^{\circ}$E
and $200^{\circ}$E-$255^{\circ}$E were used. Relative
deviations of perturbed NmF2 from their respective
quiet-time values were considered. Long-lasting negative
storm effects were the dominant characteristic observed at
middle latitudes, which occurred since the main phase of the
storm. In general, the most significant negative
disturbances were observed at middle-high latitudes. In the
longitudinal sectors in which the storm started at day-time
and pre-dusk hours, positive storm effects at middle and low
latitudes were observed during the main phase. The role of
some physical mechanisms to explain the ionospheric effects
is also considered.}
}
@inproceedings{manzo00,
author = {Manzo, R. and Parisi, M.},
title = {The use of fmin ionospheric frequency to forecast
geomagnetic and ionospheric storms},
booktitle = {Proc. of the 9th GIFCO Conference},
organization = {Gruppo Italiano di Fisica Cosmica},
year = {2000},
month = may,
address = {Lecce, Italy},
ukssdc_d = {}
}
@inproceedings{manzo00:_geomag,
author = {Manzo, R. and Parisi, M.},
title = {Geomagnetic and ionospheric response to different
interplanetary macro-perturbations},
booktitle = {Proc. of the 9th GIFCO Conference},
organization = {Gruppo Italiano di Fisica Cosmica},
year = {2000},
month = may,
address = {Lecce, Italy},
ukssdc_d = {}
}
@article{marin00:_tenden_f2,
author = {Marin, D. and Mikhailov, A.V. and de la Morena, B.A. and
Herraiz, M.},
title = {Tendencais a largo plazo en la region F2 de ionosfera y su
relacion con la actividad geomagnetica},
journal = {Fisica de la Tierra},
pages = {263--280},
year = {2000},
volume = {12},
note = {ISSN 0214--4557},
ukssdc_d = {}
}
@article{marin01:_long_euras,
author = {Marin, D. and Mikhailov, A.V. and de la Morena, B.A. and
Herraiz, M.},
title = {Long-term hmF2 trends in the Eurasion longitudinal sector
from the ground-based ionosonde observations},
journal = {Annales Geophysicae},
year = {2001},
volume = {19},
pages = {761--772},
abstract = {The method earlier used for the foF2 long-term trends
analysis is applied to reveal hmF2 long-term trends at 27
ionosonde stations in the European and Asian longitudinal
sectors. Observed M(3000)F2 data for the last 3 solar cycles
are used to derive hmF2 trends. The majority of the studied
stations show significant hmF2 linear trends with a
confidence level of at least 95\% for the period after 1965,
with most of these trends being positive. No systematic
variation of the trend magnitude with latitude is revealed,
but some longitudinal effect does take place. The proposed
geomagnetic storm concept to explain hmF2 long-term trends
proceeds from a natural origin of the trends rather than an
artificial one related to the thermosphere cooling due to
the greenhouse effect.},
keywords = {Ionosphere (ionosphere-atmosphere interaction)},
url = {http://www.copernicus.org/EGU/annales/19/761.html},
pdf = {http://www.copernicus.org/EGU/annales/19/ag19/761.pdf},
ukssdc_d = {},
ukssdc_i = {}
}
@article{materassi2005,
author = {Materassi, M. and Mitchell, C.N.},
title = {A simulation study into constructing of the sample space for
ionospheric imaging},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2005},
volume = {67},
number = {12},
pages = {1085--1091},
abstract = {Ionospheric imaging usually involves solving an
underdetermined inversion problem. The inversion is
performed involving additional constraints to enforce
realistic profiles in the vertical. One way to incorporate
those vertical profile constraints is to perform the
inversion using Empirical Orthogonal Functions (EOFs). The
need of defining a sample space spanned by EOFs to obtain
ionospheric images yields the possibility to employ
ionosonde measurements in ionospheric tomography based on
stochastic inversion of GPS data. Here we present a
simulation study based on an existing network of GPS ground
receivers and ionosondes across Europe. The locations of the
transmitters used in the simulation are actual satellite
positions. Simulated GPS data, constructed assuming that the
ionosphere is the international reference ionosphere, are
inverted via the Multi Instrument Data Analysis System. The
sample space of this stochastic inversion is constructed
employing ionosonde measurements simulated from the same
model ionosphere. Such use of ionosonde data to construct
the sample space produces better results than without
ionosonde data.},
keywords = {Electromagnetic methods; Ionosphere; Radio propagation;
Remote sensing; Radio tomography; Data inversion},
url = {http://dx.doi.org/10.1016/j.jastp.2005.02.019},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{mcwilliams00:_cutlas_finlan_hf,
author = {McWilliams, K.A. and Yeoman, T.K. and Provan, G.},
title = {A statistical survey of dayside pulsed ionospheric flows as
seen by the CUTLASS Finland HF radar},
journal = {Annales Geophysicae},
pages = {445--453},
year = {2000},
volume = {18},
abstract = {Nearly two years of 2-min resolution data and 7- to 21-s
resolution data from the CUTLASS Finland HF radar have
undergone Fourier analysis in order to study statistically
the occurrence rates and repetition frequencies of pulsed
ionospheric flows in the noon-sector high-latitude
ionosphere. Pulsed ionospheric flow bursts are believed to
be the ionospheric footprint of newly reconnected
geomagnetic field lines, which occur during episodes of
magnetic flux transfer to the terrestrial magnetosphere -
flux transfer events or FTEs. The distribution of pulsed
ionospheric flows were found to be well grouped in the radar
field of view, and to be in the vicinity of the radar
signature of the cusp footprint. Two thirds of the pulsed
ionospheric flow intervals included in the statistical study
occurred when the interplanetary magnetic field had a
southward component, supporting the hypothesis that pulsed
ionospheric flows are a reconnection-related phenomenon. The
occurrence rate of the pulsed ionospheric flow fluctuation
period was independent of the radar scan mode. The
statistical results obtained from the radar data are
compared to occurrence rates and repetition frequencies of
FTEs derived from spacecraft data near the magnetopause
reconnection region, and to ground-based optical
measurements of poleward moving auroral forms. The
distributions obtained by the various instruments in
different regions of the magnetosphere were remarkably
similar. The radar, therefore, appears to give an unbiased
sample of magnetopause activity in its routine observations
of the cusp footprint.},
ukssdc_d = {},
uk_other = {}
}
@article{mendillo2002,
author = {Mendillo, A. and Rishbeth, H. and Roble, R.G. and Wroten,
J.},
title = {Modelling F2-layer seasonal trends and day-to-day
variability driven by coupling with the lower atmosphere},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2002},
volume = {64},
number = {18},
pages = {1911--1931},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {This paper presents results from the TIME-GCM-CCM3
thermosphere-ionosphere-lower atmosphere flux-coupled model,
and investigates how well the model simulates known F2-layer
day/night and seasonal behaviour and patterns of day-to-day
variability at seven ionosonde stations. Of the many
possible contributors to F2-layer variability, the present
work includes only the influence of 'meteorological'
disturbances transmitted from lower levels in the
atmosphere, solar and geomagnetic conditions being held at
constant levels throughout a model year. In comparison to
ionosonde data, TIME-GCM-CCM3 models the peak electron
density (NmF2) quite well, except for overemphasizing the
daytime summer/winter anomaly in both hemispheres and
seriously underestimating night NmF2 in summer. The peak
height hmF2 is satisfactorily modelled by day, except that
the model does not reproduce its observed semiannual
variation. Nighttime values of hmF2 are much too low, thus
causing low model values of night NmF2. Comparison of the
variations of NmF2 and the neutral [O/N$_{2}$] ratio supports
the idea that both annual and semiannual variations of
F2-layer electron density are largely caused by changes of
neutral composition, which in turn are driven by the global
thermospheric circulation. Finally, the paper describes and
discusses the characteristics of the F2-layer response to
the imposed 'meteorological' disturbances. The ionospheric
response is evaluated as the standard deviations of five
ionospheric parameters for each station within 11-day blocks
of data. At any one station, the patterns of variability
show some coherence between different parameters, such as
peak electron density and the neutral atomic/molecular
ratio. Coherence between stations is found only between the
closest pairs, some 2500 km apart, which is presumably
related to the scale size of the 'meteorological'
disturbances. The F2-layer day-to-day variability appears to
be related more to variations in winds than to variations of
thermospheric composition.}
}
@article{mendillo06_flares_mars,
author = {Mendillo, M. and Withers, P. and Hinson, D. and Rishbeth,
H. and Reinisch, B.},
title = {Effects of solar flares on the ionosphere of Mars},
journal = {Science},
year = 2006,
month = feb,
volume = 311,
pages = {1135--1138},
abstract = {All planetary atmospheres respond to the enhanced x-rays and
ultraviolet (UV) light emitted from the Sun during a
flare. Yet only on Earth are observations so continuous that
the consequences of these essentially unpredictable events
can be measured reliably. Here, we report observations of
solar flares, causing up to 200\% enhancements to the
ionosphere of Mars, as recorded by the Mars Global Surveyor
in April 2001. Modeling the attitude dependence of these
effects requires that relative enhancements in the soft
x-ray fluxes far exceed those in the UV.},
url = {http://dx.doi.org/10.1126/science.1122099},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{mikhailov03_trends,
author = {Mikhailov, A. V. and Morena, B. A.},
title = {Long-term trends of foE and geomagnetic activity variations},
journal = {Annales Geophysicae},
pages = {751-760},
year = {2003},
volume = {21},
number = {3},
abstract = {A relationship between foE trends and geomagnetic activity
long-term variations has been revealed for the first
time. By analogy with earlier obtained results on the foF2
trends it is possible to speak about the geomagnetic control
of the foE long-term trends as well. Periods of increasing
geomagnetic activity correspond to negative foE trends,
while these trends are positive for the decreasing phase of
geomagnetic activity. This 'natural' relationship breaks
down around 1970 (on some stations later) when pronounced
positive foE trends have appeared on most of the stations
considered. The dependence of foE trends on geomagnetic
activity can be related with nitric oxide variations at the
E-layer heights. The positive foE trends that appeared after
the 'break down' effect may also be explained by the
decrease which is not related to geomagnetic activity
variations. But negative trends or irregular foE variations
on some stations for the same time period require some
different mechanism. Chemical pollution of the lower
thermosphere due to the anthropogenic activity may be
responsible for such abnormal foE behavior after the end of
the 1960s.},
ukssdc_d = {}
}
@article{2006AnGeo..24.2533M,
author = {Mikhailov, A.V.},
title = {{Ionospheric long-term trends: can the geomagnetic control
and the greenhouse hypotheses be reconciled?}},
journal = {Annales Geophysicae},
year = 2006,
month = oct,
volume = 24,
pages = {2533-2541},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24.2533M},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {The ionospheric F2-layer parameter long-term trends are
considered from the geomagnetic control concept and the
greenhouse hypothesis points of view. It is stressed that
long-term geomagnetic activity variations are crucial for
ionosphere long-term trends, as they determine the basic
natural pattern of foF2 and hmF2 long-term variations. The
geomagnetic activity effects should be removed from the
analyzed data to obtain real trends in ionospheric
parameters, but this is not usually done. Only a
thermosphere cooling, which is accepted as an explanation
for the neutral density decrease, cannot be reconciled with
negative foF2 trends revealed for the same period. A more
pronounced decrease of the O/N2 ratio is required which is
not provided by empirical thermospheric models.
Thermospheric cooling practically cannot be seen in foF2
trends, due to a weak NmF2 dependence on neutral
temperature; therefore, foF2 trends are mainly controlled by
geomagnetic activity long-term variations. Long-term hmF2
variations are also controlled by geomagnetic activity
variations, as both parameters, NmF2 and hmF2 are related by
the F2-layer formation mechanism. But hmF2 is very sensitive
to neutral temperature changes, so strongly damped hmF2
long-term variations observed at Slough after 1972 may be
considered as a direct manifestation of the thermosphere
cooling. Earlier revealed negative hmF2 trends in western
Europe, where magnetic declination D<0 and positive trends
at the eastern stations (D>0), can be related to westward
thermospheric wind whose role has been enhanced due to a
competition between the thermosphere cooling (CO2 increase)
and its heating under increasing geomagnetic activity after
the end of the 1960s.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{mikhailov01,
author = {Mikhailov, A.V. and Marin, D.},
title = {An interpretation of the foF2 and hmF2 long-term trends in
the framework of the geomagnetic control concept},
journal = {Annales Geophysicae},
pages = {733-748},
year = {2001},
volume = {17},
number = {7},
abstract = {Earlier revealed morphological features of the foF2 and hmF2
long-term trends are interpreted in the scope of the
geomagnetic control concept based on the contemporary
F2-layer storm mechanisms. The F2-layer parameter trends
strongly depend on the long-term varying geomagnetic
activity whose effects cannot be removed from the trends
using conventional indices of geomagnetic
activity. Therefore, any interpretation of the foF2 and hmF2
trends should consider the geomagnetic effects as an
inalienable part of the trend analysis. Periods with
negative and positive foF2 and hmF2 trends correspond to the
periods of increasing or decreasing geomagnetic activity
with the turning points around 1955, and the end of 1960s
and 1980s, where foF2 and hmF2 trends change their
signs. Such variations can be explained by neutral
composition, as well as temperature and thermospheric wind
changes related to geomagnetic activity variations. In
particular, for the period of increasing geomagnetic
activity (1965-1991) positive at lower latitudes, but
negative at middle and high latitudes, foF2 trends may be
explained by neutral composition and temperature changes,
while soft electron precipitation determines nighttime
trends at sub-auroral and auroral latitudes. A pronounced
dependence of the foF2 trends on geomagnetic (invariant)
latitude and the absence of any latitudinal dependence for
the hmF2 trends are due to different dependencies of NmF2
and hmF2 on main aeronomic parameters. All of the revealed
latitudinal and diurnal foF2 and hmF2 trend variations may
be explained in the frame-work of contemporary F2-region
storm mechanisms. The newly proposed geomagnetic storm
concept used to explain F2-layer parameter long-term trends
proceeds from a natural origin of the trends rather than an
artificial one, related to the thermosphere cooling due to
the greenhouse effect. Within this concept, instead of
cooling, one should expect the thermosphere heating for the
period of increasing geomagnetic activity (1965-1991).},
ukssdc_d = {},
ukssdc_i = {}
}
@article{mikhailov2000,
author = {Mikhailov, A.V. and Marin, D.},
title = {Geomagnetic control of the foF2 long-term trends},
journal = {Annales Geophysicae},
year = {2000},
volume = {18},
number = {6},
pages = {653--665},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Further development of the method proposed by Danilov and
Mikhailov is presented. The method is applied to reveal the
foF2 long-term trends on 30 Northern Hemisphere ionosonde
stations. Most of them show significant foF2 trends. A
pronounced dependence of trend magnitude on geomagnetic
(invariant) latitude is confirmed. Periods of
negative/positive foF2 trends corresponding to the periods
of long-term increasing/ decreasing geomagnetic activity are
revealed for the first time. Pronounced diurnal variations
of the foF2 trend magnitude are found. Strong positive foF2
trends in the post-midnight-early-morning LT sector and
strong negative trends during daytime hours are found on the
sub-auroral stations for the period with increasing
geomagnetic activity. On the contrary middle and lower
latitude stations demonstrate negative trends in the
early-morning LT sector and small negative or positive
trends during daytime hours for the same period. All the
morphological features revealed of the foF2 trends may be
explained in the framework of contemporary F2-region storm
mechanisms. This newly proposed F2-layer geomagnetic storm
concept casts serious doubts on the hypothesis relating the
F2-layer parameter long-term trends to the thermosphere
cooling due to the greenhouse effect.}
}
@article{mikhailov01b,
author = {Mikhailov, A.V. and Marin, D. and Leschinskaya, T.Yu. and
Herraiz, M.},
title = {A revised approach to the foF2 long-term trends analysis},
url = {http://www.ann-geophys.net/20/1663/2002/angeo-20-1663-2002.html},
pdf = {http://www.ann-geophys.net/20/1663/2002/angeo-20-1663-2002.pdf},
journal = {Annales Geophysicae},
pages = {1663-1675},
year = {2002},
volume = {20},
abstract = {A new approach to extract foF2 long-term trends, which are
free to a great extent from solar and geomagnetic activity
effects, has been proposed. These trends are insensitive to
the phase (increasing/decreasing) of geomagnetic activity,
with long-term variations being small and insignificant for
such relatively short time periods. A small but significant
residual foF2 trend, with the slope $K_{r} = - 2.2 \times
10^{-4}$ per year, was obtained over a 55-year period (the
longest avail-able) of observations at Slough. Such small
trends have no practical importance. On the other hand,
negative (although insignificant) residual trends obtained
at 10 ionosonde stations for shorter periods (31 years) may
be considered as a manifestation of a very long-term
geomagnetic activity increase which did take place during
the 20th century. All of the revealed foF2 long-term
variations (trends) are shown to have a natural origin
related to long-term variations in solar and geomagnetic
activity. There is no indication of any manmade foF2
trends.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{minnis1955,
author = {Minnis, C.M.},
title = {A new index of solar activity based on ionospheric
measurements},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {310--321},
year = {1955},
volume = {7},
abstract = {The monthly mean relative sunspot number ($R_{M}$) is
assumed to contain a component ($R_{v}$) which has a
one-to-one correlation with the critical frequency of the
$F_{2}$-layer in an undisturbed ionosphere and which is,
therefore, an idealized index of solar activity. The
residual component ($R_{x}$) may be regarded as an error
which has a Standard Deviation of about 20 per cent. A new
index ($I_{F2}$) has been constructed for the period
1938--1954; like $R_{M}$, it can also be regarded as giving
an approximate value of $R_{v}$, but its residual error
component ($R_{z}$) has an S.D. which is only about one
tenth that of $R_{x}$. The magnitude of $I_{F2}$, for a
given month is computed from the mean noon critical
frequencies in the $F_{2}$-layer at Slough, Huancayo, and
Watheroo, which are normally available within a few weeks of
the end of each month. The index is based, in effect, on a
calibration of the $F_{2}$-layer critical frequencies at
these observatories in terms of $R_{v}$, using data
extending back as far as possible. Precautions have been
taken to reduce to negligible proportions the effects of
ionospheric disturbances on the magnitude of the new index.},
url = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VSV-48889VG-PJ&_user=910841&_coverDate=12%2F31%2F1955&_fmt=abstract&_orig=search&_cdi=6272&view=c&_acct=C000047841&_version=1&_urlVersion=0&_userid=910841&md5=7db217168ff0e0535edaf92ff5e68c3b&ref=full},
ukssdc_d = {},
pdf = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VSV-48889VG-PJ-1&_cdi=6272&_user=910841&_orig=search&_coverDate=12%2F31%2F1955&_sk=999929999&view=c&chp=dGLzVtz-zSkzS&md5=3fdc865cc4c3efb6236e22a2e7e7a6c1&ie=/sdarticle.pdf},
ukssdc_i = {},
doi = {10.1016/0021-9169(55)90136-7}
}
@article{minnis1960,
author = {Minnis, C.M. and Bazzard, G.H.},
title = {A monthly ionospheric index of solar activity based on
F2-layer ionization at eleven stations},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {297--305},
year = {1960},
volume = {18},
number = {4},
abstract = {A monthly index has been constructed, for the period 1938 to
date, using monthly mean or median noon values of foF2 at
eleven widely-distributed stations. The correlation between
foF2 at noon and this index is significantly greater than
that between foF2 and either the 3 month weighted mean
sunspot number or the monthly mean solar radio noise flux at
2800 Mc/s. Numerical estimates have been made of the errors
incurred in forecasting noon and midnight foF2 several
months ahead using these three indices as guides to the
trend of solar activity.},
ukssdc_d = {},
ukssdc_i = {},
doi = {10.1016/0021-9169(60)90113-6},
url = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VSV-487CYRS-6D&_user=910841&_coverDate=08%2F31%2F1960&_alid=1658706587&_rdoc=1&_fmt=high&_orig=search&_origin=search&_zone=rslt_list_item&_cdi=6272&_sort=r&_st=13&_docanchor=&view=c&_ct=158&_acct=C000047841&_version=1&_urlVersion=0&_userid=910841&md5=94419fca51e75a9613408276c3e230c6&searchtype=a}
}
@article{mizrahi01:_statis,
author = {Mizrahi, E. and Bilge, A.H. and Tulunay, Y.K.},
title = {Statistical properties of the deviations of foF2 from
monthly medians},
journal = {Annali di Geofisica},
year = {2001},
ukssdc_d = {}
}
@article{2006AnGeo..24..961M,
author = {Morley, S.K. and Lockwood, M.},
title = {A numerical model of the ionospheric signatures of
time-varying magnetic reconnection: III. Quasi-instantaneous
convection responses in the Cowley-Lockwood paradigm},
journal = {Annales Geophysicae},
year = 2006,
month = may,
volume = 24,
pages = {961-972},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24..961M},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {Using a numerical implementation of the cowlock92 model of
flow excitation in the magnetosphere-ionosphere (MI) system,
we show that both an expanding (on a ~12-min timescale) and
a quasi-instantaneous response in ionospheric convection to
the onset of magnetopause reconnection can be accommodated
by the Cowley-Lockwood conceptual framework. This model has
a key feature of time dependence, necessarily considering
the history of the coupled MI system. We show that a
residual flow, driven by prior magnetopause reconnection,
can produce a quasi-instantaneous global ionospheric
convection response; perturbations from an equilibrium state
may also be present from tail reconnection, which will
superpose constructively to give a similar effect. On the
other hand, when the MI system is relatively free of
pre-existing flow, we can most clearly see the expanding
nature of the response. As the open-closed field line
boundary will frequently be in motion from such prior
reconnection (both at the dayside magnetopause and in the
cross-tail current sheet), it is expected that there will
usually be some level of combined response to dayside
reconnection.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{muhtarov01:_europ,
author = {Muhtarov, P. and Kutiev I. and Cander, L.R. and Zolesi,
B. and de Franceschi, G. and Levy, M. and Dick, M.},
title = {European ionospheric forecast and mapping},
journal = {Physics and Chemistry of the earth part C-Solar-Terrestial
and Planetary Science},
year = 2001,
volume = 26,
number = 5,
pages = {347--351},
abstract = {A new technique is developed for forecasting and
instantaneous mapping of the ionospheric parameters over
Europe, based on analytical presentation of the mapped
quantities. The diurnal and seasonal variations of the
ionospheric foF2 and M(3000)F2 parameters are represented by
a modified version of the regional model ISIRM adjusted to
the past measured data. An autoregressive extrapolation of
the data from the past month enables the 15-day-ahead
forecast of the quiet ionospheric distribution to be
performed. In addition, the short-term variations due to
geomagnetic activity are defined as a plane surface
superimposed on the quiet distribution. This correction is
obtained by two plane characteristics as functions of the
geomagnetic three-hour Kp index. In this way the 24-hour
forecast can be obtain during quiet as well as disturbed
ionospheric conditions. The corresponding EIFM software
provides a variety of options to perform the short-term
forecast depending on availability of the measured
ionospheric data and predicted Kp values.},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{muhtarov01:_geomag,
author = {Muhtarov, P. and Kutiev, I. and Cander, L.R.},
title = {Geomagnetically correlated autoregression model for
short-term prediction of ionospheric parameters},
url = {http://www.iop.org/EJ/abstract/0266-5611/18/1/304},
pdf = {http://www.iop.org/EJ/article/0266-5611/18/1/304/ip2104.pdf},
journal = {Inverse Problems},
pages = {49-65},
year = {2002},
volume = {18},
abstract = {A new method for short-term prediction of ionospheric
parameters is developed by incorporating the
cross-correlation between the ionospheric characteristic of
interest and the $A_{p}$ index into the autocorrelation
analysis. We consider the hourly time series of an
ionospheric characteristic as composed of a periodic
component and a random component. The periodic component
containing the average diurnal variation is removed by using
its relative deviations from the median values ($\Phi$),
which in the case of the critical frequency of the F2 layer,
foF2, has the form: $\Phi = (foF2 -
foF2_{med})/foF2_{med}$. The geomagnetically correlated
autoregression model (GCAM) is an extrapolation model based
on the weighted past data. The new term in the regression
equation expresses linearly the dependence of $\Phi$ on
magnetic activity by introducing a synthetic geomagnetic
index $G$, which approximates the average dependence of on
hourly interpolated $K_{p}$. Using parametric expressions of
the auto- and cross-correlation functions ensures the
statistical sufficiency in GCAM; the parameters are then
obtained by data fitting. Data from 2 years of high solar
activity (1981-2) and 2 years of low solar activity (1985-6)
were used to evaluate the prediction accuracy of GCAM. The
mean square error in per cent of the 1-day prediction of
foF2 relative to the median shows a large gain of accuracy
of GCAM in the first 8-10 h of prediction relative to the
median based prediction, a diurnal variation of errors and a
steady offset of the GCAM prediction error from the median
based prediction error. The GCAM error at the first hour is
lowest, but gradually approaches the median error with a
timescale of 8-10 h. A new error estimate, called
`prediction efficiency' that is a good indicator of
prediction performance during disturbed ionospheric
conditions is defined.},
ukssdc_d = {},
uk_other = {}
}
@article{2006AnGeo..24..901N,
author = {Nygr{\'e}n, T. and Aikio, A.T. and Voiculescu, M. and
Ruohoniemi, J.M.},
title = {{IMF effect on sporadic-E layers at two northern polar cap
sites: Part II Electric field}},
journal = {Annales Geophysicae},
year = 2006,
month = may,
volume = 24,
pages = {901-913},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24..901N},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {This paper is the second in a series on a study of the link
between IMF and sporadic-E layers within the polar cap. In
Paper I (Voiculescu et al., 2006), an analysis of the
sporadic-E data from Thule and Longyearbyen was
presented. Here we concentrate on the electric field
mechanism of sporadic-E generation. By means of model
calculations we show that the mechanism is effective even at
Thule, where the direction of the geomagnetic field departs
from vertical only by 4. The model calculations also lead to
a revision of the electric field theory. Previously, a thin
layer was assumed to grow at a convergent null in the
vertical ion velocity, which is formed when the electric
field points in the NW sector. Our calculations indicate
that in the dynamic process of vertical plasma compression,
a layer is generated at altitudes of high vertical
convergence rather than at a null. Consequently, the layer
generation is less sensitive than previously assumed to
fluctuations of the electric field direction within the NW
sector. The observed diurnal variations of sporadic-E
occurrence at Longyearbyen and Thule are compared with the
diurnal variations of the electric field, calculated using a
representative range of IMF values by means of the
statistical APL model. The results indicate that the main
features of Es occurrence can be explained by the convection
pattern controlled by the IMF. Electric fields calculated
from the IMF observations are also used for producing
distributions of sporadic-E occurrence as a function of
electric field direction at the two sites. A marked
difference between the distributions at Thule and
Longyearbyen is found. A model estimate of the occurrence
probability as a function of electric field direction is
developed and a reasonable agreement between the model and
the experimental occurrence is found. The calculation
explains the differences between the distributions at the
two sites in terms of the polar cap convection pattern. The
conclusion is that the electric field is the major cause for
sporadic-E generation and, consequently, IMF has a clear
control on the occurrence of sporadic E within the polar
cap.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{oliveros2005,
author = {Oliveros, B.M. and Hernandez R.D.M. and Saurez L.P.},
title = {On the onset and meridional propagation of the ionospheric
F2-region response to geomagnetic storms},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2005},
volume = {67},
number = {17--18},
pages = {1706--1714},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1016/j.jastp.2004.12.013},
abstract = {The meridional propagation velocities of the ionospheric
F2-region response to 268 geomagnetic storms are calculated.
Ionospheric vertical sounding data of I h time resolution
from several stations located in a longitude sector
approximately centred along the great circle that contains
both the geomagnetic poles and the geographic poles are
used. Most meridional propagation velocities from high to
low latitudes are less than 600 m/s. The smaller velocities
are typical of global neutral meridional wind circulation
and the larger are representative of traveling atmospheric
disturbances. Simultaneous disturbances at several
locations are more frequent during positive phases than
during negative phases. Negative phase meridional
propagation velocities associated with meridional neutral
winds are less frequent in the southern hemisphere when
compared with corresponding velocities observed in the
northern hemisphere. This may be related to the fact that
the distance between the geomagnetic pole and the equator is
smaller in the northern hemisphere. Most negative phase
onsets are within the 06-10 LT interval. For middle
geomagnetic latitudes a "forbidden time interval" between 11
and 14 LT is present. The positive phase onsets show the
"dusk effect".}
}
@article{onsager01:_recon,
author = {Onsager, T.G. and Scudder, J.D. and Lockwood, M. and
Russell, C.T.},
title = {Reconnection at the high-latitude magnetopause during
northward interplanetary magnetic field conditions},
journal = {Journal of Geophysical Research},
year = 2001,
month = nov,
volume = 106,
number = {A11},
pages = {25467--25488},
url = {http://dx.doi.org/10.1029/2000JA000444},
adsurl = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2001JGR...10625467O&db_key=AST},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_other = {},
abstract = {The Polar spacecraft had a prolonged encounter with the
high-latitude dayside magnetopause on May 29, 1996. This
encounter with the magnetopause occurred when the
interplanetary magnetic field was directed northward. From
the three-dimensional electron and ion distribution
functions measured by the Hydra instrument, it has been
possible to identify nearly all of the distinct boundary
layer regions associated with high-latitude
reconnection. The regions that have been identified are (1)
the cusp; (2) the magnetopause current layer; (3)
magnetosheath field lines that have interconnected in only
the Northern Hemisphere; (4) magnetosheath field lines that
have interconnected in only the Southern Hemisphere; (5)
magnetosheath field lines that have interconnected in both
the Northern and Southern Hemispheres; (6) magnetosheath
that is disconnected from the terrestrial magnetic field;
and (7) high-latitude plasma sheet field lines that are
participating in magnetosheath reconnection. Reconnection
over this time period was occurring at high latitudes over a
broad local-time extent, interconnecting the magnetosheath
and lobe and/or plasma sheet field lines in both the
Northern and Southern Hemispheres. Newly closed boundary
layer field lines were observed as reconnection occurred
first at high latitudes in one hemisphere and then later in
the other. These observations establish the location of
magnetopause reconnection during these northward
interplanetary magnetic field conditions as being at high
latitudes, poleward of the cusp, and further reinforce the
general interpretation of electron and ion phase space
density signatures as indicators of magnetic reconnection
and boundary layer formation.}
}
@incollection{opgenoorth97:_new_famil_geomag_distur_indic,
author = {Opgenoorth, H.J. and Persson, M.A.L. and Lockwood, M. and
Stamper, R. and Wild, M.N. and Pellinen, R. and Pulkkinen,
T. and Kauristie, K. and Hughes, T. and Kamide, Y.},
editor = {Lockwood, M. and Wild, M.N. and Opgenoorth, H.J.},
title = {A New Family of Geomagnetic Disturbance Indices},
booktitle = {Satellite - Ground Based Coordination Sourcebook},
pages = {49--62},
year = {1997},
publisher = {ESA},
volume = {SP-1198},
ukssdc_w = {},
ukssdc_d = {},
uk_other = {}
}
@article{2007RaSc...42S3004O,
author = {Orus, R. and Cander, L.R. and Hernandez-Pajares, M.},
title = {{Testing regional vertical total electron content maps over
Europe during the 17-21 January 2005 sudden space weather
event}},
journal = {Radio Science},
year = 2007,
month = may,
volume = 42,
pages = {3004-+},
doi = {10.1029/2006RS003515},
adsurl = {http://adsabs.harvard.edu/abs/2007RaSc...42S3004O},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {The intense level of solar activity recorded from 16 to 23
January 2005 led to a series of events with different
signatures at the Earth's ionospheric
distances. Measurements of the critical frequency of the F2
layer foF2 and the vertical total electron content (VTEC)
are used to describe the temporal and spatial electron
density distributions during this space weather event, which
gives an excellent opportunity to test regional VTEC maps
over Europe under such disturbed solar-terrestrial
conditions. In this context, the tests used to validate the
International GNSS Service (IGS) VTEC maps have been applied
to assess the accuracy of the European Rutherford Appleton
Laboratory (RAL) VTEC maps. Thus the self-consistency test
and the Jason altimeter test have been used to compare such
performances with the IGS and Universitat Politecnica de
Catalunya global ionospheric maps. The results show
discrepancies between the RAL maps and the IGS ones, which
leads to significant RMS and bias values of several total
electron content units. Moreover, in this work a kriging
technique to improve the accuracy of any regional VTEC map
is also considered, with relative improvements of the RAL
VTEC maps up to more than 20\% at the peak of the storm.},
uk_other = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{ozcan04,
author = {Ozcan, O. and Aydogdu, M.},
title = {Possible effects of the total solar eclipse of August 11,
1999 on the geomagnetic field variations over Elazig-Turkey},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
pages = {997-1000},
year = {2004},
month = {jul},
volume = {66},
number = {11},
abstract = {In this paper, the variations of the magnetic field, due to
current flowing in the ionospheric E-region over
Elazig-Turkey during the August 11, 1999 total solar eclipse
have been computed. It is shown that the solar eclipse has
no significant effects on the north-south component of the
magnetic field. However, the westward component of the
magnetic field is decreased by the solar eclipse. Therefore,
we would expect that the change in the magnetic field in
E-region during the solar eclipse would modify the
geomagnetic field at ground level.},
ukssdc_d = {}
}
@article{ozguc98:_istan,
author = {Ozguc, A. and Atac, T. and Tulunay, Y. and Stanislawska, I.},
title = {The ionospheric foF2 data over Istanbul and their response
to solar activity for the years 1964-1969 and 1993},
journal = {Studia Geophysica et Geodaetica},
pages = {112--118},
year = {1998},
volume = {42},
number = {2},
ukssdc_d = {}
}
@article{ozguc98:_examin,
author = {Ozguc, A. and Tulunay, Y. and Atac, T.},
title = {Examination of the solar cycle variation of foF2 by using
solar flare index for the cycle 21},
journal = {Advances in Space Research},
pages = {139--142},
year = {1998},
month = {jan},
volume = {22},
number = {1},
abstract = {For solar cycle 21 (1976 - 1986) the variation of monthly
mean values of noon-time foF2 at Slough, Rome, and Manila
are examined by using solar flare index and geomagnetic Ap
index. A single regression analysis for dependence of foF2
on solar flare index shows better matching. Moreover, less
hysteresis effect is seen when we use solar flare index
instead of other solar indices. Thus, for making prediction,
one needs to take into account just the solar flare index
and not the solar flare index and geomagnetic Ap index
simultaneously.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{perrone01:_pc_ae,
author = {Perrone, L. and De Franceschi, G. and Gulyaeva, T.L.},
title = {The time-weighted magnetic indices ap(\tau), PC(\tau),
AE(\tau) and their correlation to the southern high-latitude
ionosphere},
journal = {Phys. Chem. Earth (C)},
pages = {325--330},
year = {2001},
volume = {26},
number = {5},
ukssdc_d = {}
}
@article{peitrella05,
author = {Pietrella, M. and Perrone, L.},
title = {Instantaneous space-weighted ionospheric regional model for
instantaneous mapping of the critical frequency of the F2
layer in the European region},
journal = {Radio Science},
year = {2005},
volume = {40},
number = {1},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2003RS003008},
abstract = {An instantaneous space-weighted ionospheric regional model
(ISWIRM) for the regional now-casting of the critical
frequency of the F2 layer ( foF2) has been developed. The
geographical area of applicability of the model is ranged
between $35^{\circ}$N - $70^{\circ}$N and $5^{\circ}$W -
$40^{\circ}$E. Inside this region the hourly values of foF2
are obtained, correcting the monthly medians values of foF2
predicted by the space-weighted ionospheric local model (
SWILM) on the basis of hourly observations of foF2 coming
from four reference stations ( Rome, Chilton, Lycksele, and
Loparskaya ( or Sodankyla)). The performance of the model,
evaluated at four testing stations ( Tortosa, Juliusruh,
Uppsala, and Kiruna) during some periods characterized by
strong solar and geomagnetic activity, can be considered
satisfactory, given that the hourly values of the residuals
are almost always below 1 MHz. A comparison between ISWIRM's
performance using manually validated and autoscaled data of
foF2 and SWILM's performance was made for two disturbed
periods. One example of instantaneous ionospheric mapping of
foF2 relative to the selected disturbed periods is also
shown.}
}
@article{pirog01:_asia_pacif_ocean,
author = {Pirog, O.M. and Polekh, N.M. and Chictyakova, L.V.},
title = {A study of ionospheric reaction to magnetic storms in the
Asia-Pacific Ocean},
journal = {Geomagnetizm i aeronomiya},
pages = {67--75},
year = {2001},
volume = {41},
ukssdc_d = {}
}
@article{pirog01:_longit_f,
author = {Pirog, O.M. and Polekh, N.M. and Chictyakova, L.V.},
title = {Longitudinal variation of critical frequencies in polar
F-region},
journal = {Advances in Space Research},
pages = {1395--1398},
year = {2001},
volume = {27},
number = {8},
abstract = {Based on data from a network of ionospheric stations located
in the range of geographic longitudes
$19^{\circ}$-$285^{\circ}$ and invariant latitudes
$53^{\circ}$-$70^{\circ}$N we have investigated diurnal
behaviour variations in F2-layer critical frequencies for
different seasons and different levels of solar
activity. The study revealed that the longitudinal effect in
diurnal foF2 variations is most conspicuous in the
summertime at the invariant latitude about $55-57^{\circ}$N
and manifests itself in the shift of the foF2 maximum into
the evening and night-time hours on the Yakutsk
($129.6^{\circ}$) and Ottawa ($284^{\circ}$) meridians in
the region of westward declination. It is likely that such a
behaviour of foF2 is conditioned by a change in the dynamic
regime of the high-latitude ionosphere associated with the
magnetic anomaly.},
ukssdc_d = {}
}
@article{pulkkinen01:_sun_g_connec_time_scales,
author = {Pulkkinen, T.I. and Nevanlinna, H. and Pulkkinen, P.J. and
Lockwood M.},
title = {The Sun-Earth Connection in Time Scales from Years to Decades and Centuries},
journal = {Space Science Reviews},
year = 2001,
volume = 95,
number = {1-2},
pages = {625--637},
month = jan,
uk_other = {},
ukssdc_d = {},
ukssdc_w = {},
abstract = {The Sun--Earth connection is studied using long-term
measurements from the Sun and from the Earth. The auroral
activity is shown to correlate to high accuracy with the
smoothed sunspot numbers. Similarly, both geomagnetic
activity and global surface temperature anomaly can be
linked to cyclic changes in the solar activity. The
interlinked variations in the solar magnetic activity and in
the solar irradiance cause effects that can be observed both
in the Earth's biosphere and in the electromagnetic
environment. The long-term data sets suggest that the
increase in geomagnetic activity and surface temperatures
are related (at least partially) to longer-term solar
variations, which probably include an increasing trend
superposed with a cyclic behavior with a period of about 90
years.}
}
@article{reinisch04:automated_ionospheric_digisonde_network,
author = {Reinisch, B.W. and Galkin, I.A. and Khmyrov, G. and Kozlov,
A. and Kitrosser, D.F.},
title = {Automated collection and dissemination of ionospheric data
from the digisonde network},
journal = {Advances in Space Research},
year = 2004,
volume = 2,
pages = {241--247},
abstract = {The growing demand for fast access to accurate ionospheric
electron density profiles and ionospheric characteristics
calls for efficient dissemination of data from the many
ionosondes operating around the globe. The global digisonde
network with over 70 stations takes advantage of the
Internet to make many of these sounders remotely accessible
for data transfer and control. Key elements of the digisonde
system data management are the visualization and editing
tool SAO Explorer, the digital ionogram database DIDBase,
holding raw and derived digisonde data under an
industrial-strength database management system, and the
automated data request execution system ADRES.},
url = {http://www.copernicus.org/URSI/ars/ARS_2_1/241.pdf},
ukssdc_d = {},
ukssdc_i = {}
}
@article{2006JATP...68..469R,
author = {Rishbeth, H.},
title = {{F-region links with the lower atmosphere?}},
journal = {Journal of Atmospheric and Terrestrial Physics},
year = 2006,
month = feb,
volume = 68,
pages = {469-478},
doi = {10.1016/j.jastp.2005.03.017},
adsurl = {http://adsabs.harvard.edu/abs/2006JATP...68..469R},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{rishbeth00:_equat_f,
author = {Rishbeth, H.},
title = {The equatorial F-layer: progress and puzzles},
journal = {Annales Geophysicae},
pages = {730--739},
year = {2000},
volume = {18},
number = {7},
abstract = {This work reviews some aspects of the ionospheric F-layer in
the vicinity of the geomagnetic equator. Starting with a
historical introduction, brief summaries are given of the
physics that makes the equatorial ionosphere so interesting,
concentrating on the large-scale structure rather than the
smaller-scale instability phenomena. Several individual
topics are then discussed, including eclipse effects, the
asymmetries of the `equatorial trough', variations with
longitude, the semiannual variation, the effects of the
global thermospheric circulation, and finally the equatorial
neutral thermosphere, including `superrotation' and possible
topographic influences.},
ukssdc_d = {},
uk_first = {}
}
@article{rishbeth04:_quest_f2,
author = {Rishbeth, H.},
title = {Questions of the equatorial F2-layer and thermosphere},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = 2004,
volume = 66,
number = 17,
pages = {1669--1674},
month = nov,
url = {http://dx.doi.org/10.1016/j.jastp.2004.07.008},
abstract = {This paper briefly reviews questions relating to the
equatorial thermosphere and ionosphere that do not seem to
be fully solved. They include the effect of night E-region
conductivity on F-region electrodynamics, annual and
semiannual variations of F2-layer electron density, and
superrotation' of the thermosphere. New results are
presented on the neutral gas composition of the equatorial
thermosphere, showing a pronounced annual variation.},
ukssdc_d = {},
uk_first = {}
}
@article{rishbeth98:_how_f2,
author = {Rishbeth, H.},
title = {How the thermospheric circulation affects the ionospheric
F2-layer},
journal = {Journal of Atmospheric and Terrestrial Physics},
pages = {1385--1402},
year = {1998},
volume = {60},
number = {14},
abstract = {After a historical introduction in Section 1, the paper
summarizes in Section 2 the physical principles that govern
the behaviour of the ionospheric F2-layer. Section 3 reviews
the physics of thermospheric dynamics at F-layer heights,
and how the thermospheric winds affect the neutral chemical
composition. Section 4 discusses the seasonal, annual and
semiannual variations of the quiet F2 peak at midlatitudes,
while Section 5 deals with storm conditions. The paper
concludes by summing up the state of understanding of
F2-layer variations and reviewing some important principles
that apply to ionospheric studies},
ukssdc_d = {},
uk_first = {}
}
@article{rishbeth90:_model_f2,
author = {Rishbeth, H. and Edwards, R.},
title = {Modeling the F2 layer peak height in terms of atmospheric
pressure},
journal = {Radio Science},
pages = {757--769},
year = {1990},
volume = {25},
number = {5},
ukssdc_d = {},
uk_first = {}
}
@article{rishbeth01:_patterns_f2_variability,
author = {Rishbeth, H. and Mendillo, M.},
title = {Patterns of F2-layer variability},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
year = {2001},
volume = {63},
number = {15},
pages = {1661--1680},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {The ionosphere displays variations on a wide range of
time-scales, ranging from operational time-scales of hours
and days up to solar cycles and longer. We use ionosonde
data from thirteen stations to study the day-to-day
variability of the peak F2-layer electron density, NmF2,
which we use to define quantitative descriptions of
variability versus local time, season and solar cycle. On
average, for years of medium solar activity (solar
decimetric flux approximately 140 units), the daily
fluctuations of NmF2 have a standard deviation of 20\% by
day, and 33\% by night. We examine and discuss the patterns
of behaviour of ionospheric and geomagnetic variability, in
particular the equinoctial peaks. For further analysis we
concentrate on one typical midlatitude station, Slough. We
find that the standard deviations of day-to-day and
night-to-night values of Slough NmF2 at first increase with
increasing length of the dataset, become fairly constant at
lengths of 10-20 days and then increase further (especially
at equinox) because of seasonal changes. We found some
evidence of two-day waves, but they do not appear to be a
major feature of Slough's F2 layer. Putting together the
geomagnetic and ionospheric data, and taking account of the
day-to-day variability of solar and geomagnetic parameters,
we find that a large part of F2-layer variability is linked
to that of geomagnetic activity, and attribute the rest to
'meteorological' sources at lower levels in the
atmosphere. We suggest that the greater variability at night
is due to enhanced auroral energy input, and to the lack of
the strong photochemical control of the F2-layer that exists
by day.}
}
@article{rishbeth04,
author = {Rishbeth, H. and Mendillo, M.},
title = {Ionospheric layers of Mars and Earth},
journal = {Planetary and Space Science},
pages = {849-852},
year = {2004},
month = {aug},
volume = {52},
number = {9},
url = {http://dx.doi.org/10.1016/j.pss.2004.02.007},
abstract = {We compare the electron densities of two martian ionospheric
layers, which we call M1 and M2, measured by Mars Global
Surveyor during 9-27 March 1999, with the electron densities
of the terrestrial E and F1 layers derived from ionosonde
data at six sites. The day-to-day variations are all linked
to changes in solar activity, and provide the opportunity of
making the first simultaneous study of four photochemical
layers in the solar system. The `ionospheric layer index',
which we introduce to characterize ionospheric layers in
general, varies between layers because different atmospheric
chemistry and solar radiations are involved. The M2 and F1
layer peaks occur at similar atmospheric pressure levels,
and the same applies to the M1 and E layers.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{rishbeth00:_annual_f2,
author = {Rishbeth, H. and Muller-Wodarg, I.C.F. and Zou, L. and
Fuller-Rowell, T.J. and Millward, G.H. and Moffett, R.J. and
Idenden, D.W. and Aylward, A.D.},
title = {Annual and semiannual variations in the ionospheric
F2-layer: II. Physical discussion},
journal = {Annales Geophysicae},
pages = {945--956},
year = {2000},
volume = {18},
number = {8},
abstract = {The companion paper by Zou et al. shows that the annual and
semiannual variations in the peak F2-layer electron density
(NmF2) at midlatitudes can be reproduced by a coupled
thermosphere-ionosphere computational model (CTIP), without
recourse to external influences such as the solar wind, or
waves and tides originating in the lower atmosphere. The
present work discusses the physics in greater detail. It
shows that noon NmF2 is closely related to the ambient
atomic/molecular concentration ratio, and suggests that the
variations of NmF2 with geographic and magnetic longitude
are largely due to the geometry of the auroral ovals. It
also concludes that electric fields play no important part
in the dynamics of the midlatitude thermosphere. Our
modelling leads to the following picture of the global
three-dimensional thermospheric circulation which, as
envisaged by Duncan, is the key to explaining the F2-layer
variations. At solstice, the almost continuous solar input
at high summer latitudes drives a prevailing
summer-to-winter wind, with upwelling at low latitudes and
throughout most of the summer hemisphere, and a zone of
downwelling in the winter hemisphere, just equatorward of
the auroral oval. These motions affect thermospheric
composition more than do the alternating day/night
(up-and-down) motions at equinox. As a result, the
thermosphere as a whole is more molecular at solstice than
at equinox. Taken in conjunction with the well-known
relation of F2-layer electron density to the
atomic/molecular ratio in the neutral air, this explains the
F2-layer semiannual effect in NmF2 that prevails at low and
middle latitudes. At higher midlatitudes, the seasonal
behaviour depends on the geographic latitude of the winter
downwelling zone, though the effect of the composition
changes is modified by the large solar zenith angle at
midwinter. The zenith angle effect is especially important
in longitudes far from the magnetic poles. Here, the
downwelling occurs at high geographic latitudes, where the
zenith angle effect becomes overwhelming and causes a
midwinter depression of electron density, despite the
enhanced atomic/molecular ratio. This leads to a semiannual
variation of NmF2. A different situation exists in winter at
longitudes near the magnetic poles, where the downwelling
occurs at relatively low geographic latitudes so that solar
radiation is strong enough to produce large values of
NmF2. This circulation-driven mechanism provides a
reasonably complete explanation of the observed pattern of
F2 layer annual and semiannual quiet-day variations.},
ukssdc_d = {},
uk_first = {}
}
@article{2006AnGeo..24.3293R,
author = {Rishbeth, H. and M{\"u}ller-Wodarg, I.C.F.},
title = {Why is there more ionosphere in January than in July? The
annual asymmetry in the F2-layer},
journal = {Annales Geophysicae},
year = 2006,
month = dec,
volume = 24,
pages = {3293-3311},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24.3293R},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {Adding together the northern and southern hemisphere values
for pairs of stations, the combined peak electron density
NmF2 is greater in December-January than in June-July. The
same applies to the total height-integrated electron
content. This "F2-layer annual asymmetry" between northern
and southern solstices is typically 30\%, and thus greatly
exceeds the 7\% asymmetry in ion production due to the annual
variation of Sun-Earth distance. Though it was noticed in
ionospheric data almost seventy years ago, the asymmetry is
still unexplained. Using ionosonde data and also values
derived from the International Reference Ionosphere, we show
that the asymmetry exists at noon and at midnight, at all
latitudes from equatorial to sub-auroral, and tends to be
greater at solar minimum than solar maximum. We find a
similar asymmetry in neutral composition in the MSIS model
of the thermosphere. Numerical computations with the
Coupled Thermosphere-Ionosphere-Plasmasphere (CTIP) model
give a much smaller annual asymmetry in electron density and
neutral composition than is observed. Including mesospheric
tides in the model makes little difference. After
considering possible explanations, which do not account for
the asymmetry, we are left with the conclusion that
dynamical influences of the lower atmosphere (below about 30
km), not included in our computations, are the most likely
cause of the asymmetry.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{rishbeth00_semiann,
author = {Rishbeth, H. and Sedgemore-Schulthess, K.J.F. and Ulich, T.},
title = {Semiannual and annual variations in the height of the
ionospheric F2-peak},
journal = {Annales Geophysicae},
pages = {285--299},
year = {2000},
volume = {18},
number = {3},
abstract = {Ionosonde data from sixteen stations are used to study the
semiannual and annual variations in the height of the
ionospheric F2-peak, hmF2. The semiannual variation, which
peaks shortly after equinox, has an amplitude of about 8 km
at an average level of solar activity (10.7 cm flux = 140
units), both at noon and midnight. The annual variation has
an amplitude of about 11 km at northern midlatitudes,
peaking in early summer; and is larger at southern stations,
where it peaks in late summer. Both annual and semiannual
amplitudes increase with increasing solar activity by day,
but not at night. The semiannual variation in hmF2 is
unrelated to the semiannual variation of the peak electron
density NmF2, and is not reproduced by the CTIP and TIME-GCM
computational models of the quiet-day thermosphere and
ionosphere. The semiannual variation in hmF2 is
approximately "isobaric", in that its amplitude corresponds
quite well to the semiannual variation in the height of
fixed pressure-levels in the thermosphere, as represented by
the MSIS empirical model. The annual variation is not
"isobaric". The annual mean of hmF2 increases with solar
10.7 cm flux, both by night and by day, on average by about
0.45 km/flux unit, rather smaller than the corresponding
increase of height of constant pressure-levels in the MSIS
model. The discrepancy may be due to solar-cycle variations
of thermospheric winds. Although geomagnetic activity, which
affects thermospheric density and temperature and therefore
hmF2 also, is greatest at the equinoxes, this seems to
account for less than half the semiannual variation of
hmF2. The rest may be due to a semiannual variation of tidal
and wave energy transmitted to the thermosphere from lower
levels in the atmosphere.},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
@article{Rishbeth20091096,
title = {The solar-terrestrial event of 23 February 1956},
journal = {Advances in Space Research},
volume = 44,
number = 10,
pages = {1096 - 1106},
year = 2009,
note = {Cosmic Rays From Past to Present},
issn = {0273-1177},
doi = {10.1016/j.asr.2009.06.020},
url = {http://www.sciencedirect.com/science/article/B6V3S-4WP47R8-3/2/7d0355551eaf8eef42159a5de7e3006c},
author = {Rishbeth, H. and Shea, M.A. and Smart, D.F.},
keywords = {23 February 1956},
keywords = {Solar activity},
keywords = {Solar-terrestrial events},
keywords = {Ground-level enhancements (GLE)},
keywords = {Ionosphere},
keywords = {Personal reminiscences},
abstract = {The solar flare of 23 February 1956 and the resulting
geophysical disturbance ranks as one of the most remarkable
solar-terrestrial events of the twentieth century. It
sparked many papers and has seldom been equalled. Fifty
years after the International Geophysical Year, it seems
timely to review the observations of the event from today's
perspective, and to draw on the recollections of scientists
who were active at the time.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{rouillard03:_oscil,
author = {Rouillard, A. and Lockwood, M.},
title = {Oscillations in the open solar magnetic flux with period
1.68 years: imprint on galactic cosmic rays and implications
for heliospheric shielding},
journal = {EGS - AGU - EUG Joint Assembly, Abstracts from the meeting
held in Nice, France, 6 - 11 April 2003, abstract \#6579},
year = 2003,
month = apr,
pages = {6579-+},
url = {http://adsabs.harvard.edu/cgi-bin/nph-bib_query?bibcode=2003EAEJA.....6579L&db_key=PHY},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
uk_other = {},
abstract = {A full understanding of how the heliospheric modulates the
fluxes of galactic cosmic rays reaching the Earth is vital,
not only for studies of their origin, acceleartion and
propagation in our galaxy, but also for predicting their
effects on modern technology and Earth's environment and
organisms. We here use a strong 1.68-year oscillation in
both GCR fluxes and the open solar magnetic flux to define
where and how the heliospheric field shields Earth from GCRs
and report an inward motion of that shield over the past 30
years.}
}
@article{2004AnGeo..22.4381R,
author = {Rouillard, A.P. and Lockwood, M.},
title = {{Oscillations in the open solar magnetic flux with a period
of 1.68years: imprint on galactic cosmic rays and
implications for heliospheric shielding}},
journal = {Annales Geophysicae},
year = 2004,
month = dec,
volume = 22,
pages = {4381-4395},
adsurl = {http://adsabs.harvard.edu/abs/2004AnGeo..22.4381R},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {An understanding of how the heliosphere modulates galactic
cosmic ray (GCR) fluxes and spectra is important, not only
for studies of their origin, acceleration and propagation in
our galaxy, but also for predicting their effects (on
technology and on the Earth's environment and organisms) and
for interpreting abundances of cosmogenic isotopes in
meteorites and terrestrial reservoirs. In contrast to the
early interplanetary measurements, there is growing evidence
for a dominant role in GCR shielding of the total open
magnetic flux, which emerges from the solar atmosphere and
enters the heliosphere. In this paper, we relate a strong
1.68-year oscillation in GCR fluxes to a corresponding
oscillation in the open solar magnetic flux and infer
cosmic-ray propagation paths confirming the predictions of
theories in which drift is important in modulating the
cosmic ray flux.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{2007JGRA..11205103R,
author = {Rouillard, A.P. and Lockwood, M. and Finch, I.},
title = {{Centennial changes in the solar wind speed and in the open
solar flux}},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2007,
month = may,
volume = 112,
number = {A11},
pages = {5103-+},
doi = {10.1029/2006JA012130},
adsurl = {http://adsabs.harvard.edu/abs/2007JGRA..11205103R},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {We use combinations of geomagnetic indices, based on both
variation range and hourly means, to derive the solar wind
flow speed, the interplanetary magnetic field strength at 1
AU and the total open solar flux between 1895 and the
present. We analyze the effects of the regression procedure
and geomagnetic indices used by adopting four analysis
methods. These give a mean interplanetary magnetic field
strength increase of $45.1 \pm 4.5\%$ between 1903 and 1956,
associated with a $14.4 \pm 0.7\%$ rise in the solar wind
speed. We use averaging timescales of 1 and 2 days to allow
for the difference between the magnetic fluxes threading the
coronal source surface and the heliocentric sphere at 1
AU. The largest uncertainties originate from the choice of
regression procedure: the average of all eight estimates of
the rise in open solar flux is $73.0 \pm 5.0\%$, but the
best procedure, giving the narrowest and most symmetric
distribution of fit residuals, yields $87.3 \pm 3.9\%$.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@unpublished{saunders1993,
author = {Saunders, M.A. and Lockwood, M. and Wild, M.N.},
title = {The semi-annual variation in great geomagnetic storms},
year = {1993},
month = mar,
note = {Submitted to Annales Geophysicae},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{schunk04,
author = {Schunk, R. W. and Scherliess, L. and Sojka, J. J. and
Thompson, D. C. and Anderson, D. N. and Codrescu, M. and
Minter, C. and Fuller-Rowell, T. J. and Heelis, R. A. and
Hairston, M. and Howe, B. M.},
title = {Global Assimilation of Ionospheric Measurements (GAIM)},
journal = {Radio Science},
year = {2004},
volume = {39},
abstract = {The ionosphere is a highly dynamic medium that exhibits
weather disturbances at all latitudes, longitudes, and
altitudes, and these disturbances can have detrimental
effects on both military and civilian systems. In an effort
to mitigate the adverse effects, we are developing a
physics-based data assimilation model of the ionosphere and
neutral atmosphere called the Global Assimilation of
Ionospheric Measurements (GAIM). GAIM will use a
physics-based ionosphere-plasmasphere model and a Kalman
filter as a basis for assimilating a diverse set of
real-time (or near real-time) measurements. Some of the data
to be assimilated include in situ density measurements from
satellites, ionosonde electron density profiles, occultation
data, ground-based GPS total electron contents (TECs),
two-dimensional ionospheric density distributions from
tomography chains, and line-of-sight UV emissions from
selected satellites. When completed, GAIM will provide
specifications and forecasts on a spatial grid that can be
global, regional, or local. The primary output of GAIM will
be a continuous reconstruction of the three-dimensional
electron density distribution from 90 km to geosynchronous
altitude (35,000 km). GAIM also outputs auxiliary
parameters, including NmF2, hmF2, NmE, hmE, and slant
and vertical TEC. Furthermore, GAIM provides global
distributions for the ionospheric drivers (neutral winds and
densities, magnetospheric and equatorial electric fields,
and electron precipitation patterns). In its specification
mode, GAIM yields quantitative estimates for the accuracy of
the reconstructed ionospheric densities.},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/2002RS002794}
}
@article{seah97:_incid_acute_primar_angle_glauc_singap,
author = {Seah, Steve K.L. and Foster, Paul J. and Chew, Paul T.K. and
Jap, Aliza and Oen, Francis and Fam, Han Bor and Lim, Arthur
S.M.},
title = {Incidence of Acute Primary Angle-closure Glaucoma in
Singapore},
journal = {Arch Opthalmol},
pages = {1436--1440},
year = {1997},
month = nov,
volume = {115},
number = {11},
ukssdc_d = {}
}
@article{secan97:_statis_studies_effec_sunsp_number,
author = {Secan, J. and Wilkinson, P.J.},
title = {Statistical Studies of an Effective Sunspot Number},
journal = {Radio Science},
pages = {1717},
year = {1997},
volume = {32},
number = {4},
abstract = {Two decades ago, the U.S. Air Force Air Weather Service
space forecasting group began generating what was termed an
effective sunspot number ($SSN_{e}$) by fitting a model of
the critical frequency of the $F_{2}$ layer ($f_{o}F_{2}$)
to observed $f_{o}F_{2}$ values. Initially a preprocessing
step in a larger analysis package, this parameter has taken
on a life of its own and is now used in various applications
for both forecasts and specification of the global
$f_{o}F_{2}$ field. This paper describes the various ways in
which this parameter is calculated, investigates the
behavior of this parameter over solar cycle 21 (1976 through
1986), and compares it with other solar-ionospheric indices,
including $R_{12}$, $I_{F2}$, $I_{G}$, and the Ionospheric
Prediction Service (IPS) $T$ index.},
url = {http://www.agu.org/pubs/crossref/1997/97RS01350.shtml},
ukssdc_d = {}
}
@article{2006AnGeo..24.2347S,
author = {Senior, A. and Kosch, M.J. and Yeoman, T.K. and Rietveld,
M.T. and McCrea, I.W.},
title = {{Effects of high-latitude atmospheric gravity wave
disturbances on artificial HF radar backscatter}},
journal = {Annales Geophysicae},
year = 2006,
month = sep,
volume = 24,
pages = {2347-2361},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24.2347S},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {Observations of HF radar backscatter from artificial
field-aligned irregularities in an ionosphere perturbed by
travelling disturbances due to atmospheric gravity waves are
presented. Some features of the spatio-temporal structure of
the artificial radar backscatter can be explained in terms
of the distortion of the ionosphere resulting from the
travelling disturbances. The distorted ionosphere can allow
the HF pump wave to access upper-hybrid resonance at larger
distances from the transmitter than are normally observed
and can also prevent the pump wave reaching this resonance
at close distances. The variation in altitude of the
irregularities sometimes results in a significant variation
in the elevation angle of arrival of the backscattered
signal at the radar implying that the radar "sees" a target
moving in altitude. We suggest that this may be evidence of
off-orthogonal scattering from the irregularities. },
uk_other = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{sethi2002,
author = {Sethi, N.K. and Goel, M.K. and Mahajan, K.K.},
title = {Solar Cycle variations of foF2 from IGY to 1990},
journal = {Annales Geophysicae},
volume = {20},
number = {10},
year = {2002},
pages = {1677--1685},
ukssdc_d = {},
ukssdc_i = {},
abstract = {Noontime monthly median values of F2-layer critical
frequency foF2 (m) for some ionospheric stations
representing low- and mid-latitudes are examined for their
dependence on solar activity for the years 1957 (IGY) to
1990. This is the period for which ionospheric data in
digital form is available in two CD-ROMs at the World Data
Center, Boulder. It is observed that at mid-latitudes, foF2
(m) shows nearly a linear relationship with R12 (the
12-month running average of the Zurich sunspot number),
though this relation is nonlinear for low-latitudes. These
results indicate some departures from the existing
information often used in theoretical and applied areas of
space research.}
}
@article{shastri98:_quant_f2,
author = {Shastri, S. and Gulyaeva, T.L.},
title = {Quantitative estimates of probability for day-to-day
variability of F2-peak},
journal = {Indian Journal of Radio \& Space Physics},
pages = {173--178},
year = {1998},
volume = {27},
number = {4},
ukssdc_d = {}
}
@incollection{smith1981,
author = {Smith, P.A.},
editor = {Lucas, D.L.},
title = {Suitable Values of Solar Indices - IF2},
booktitle = {Procedures for HF Broadcasting},
year = {1981},
publisher = {CCIR},
ukssdc_d = {}
}
@article{stamper1996,
author = {Stamper, R.},
title = {Improved prediction of I_{F2} and I_{G} indices using neural
networks},
journal = {IEEE Proc.-Microw. Antennas Propag.},
pages = {341--346},
year = {1996},
month = aug,
volume = {143},
number = {4},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{stamper98:_solar_causes_long_term_increas_geomag_activ,
author = {Stamper, R. and Lockwood, M. and Wild, M.N. and Clark,
T.D.G.},
title = {Solar Causes of the Long-Term Increase in Geomagnetic
Activity},
journal = {Journal of Geophysical Research},
pages = {28325--28342},
year = {1999},
month = dec,
volume = {104},
number = {A12},
ukssdc_w = {},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {},
abstract = {We analyze the causes of the century-long increase in
geomagnetic activity, quantified by annual means of the {\it
aa} index, using observations of interplanetary space,
galactic cosmic rays, the ionosphere, and the auroral
electrojet, made during the last three solar cycles. The
effects of changes in ionospheric conductivity, the Earth's
dipole tilt, and magnetic moment are shown to be small; only
changes in near-Earth interplanetary space make a
significant contribution to the long-term increase in
activity. We study the effects of the interplanetary medium
by applying dimensional analysis to generate the optimum
solar wind-magnetosphere energy coupling function, having an
unprecedentedly high correlation coefficient of
0.97. Analysis of the terms of the coupling function shows
that the largest contributions to the drift in activity over
solar cycles 20--22 originate from rises in the average
interplanetary magnetic field (IMF) strength, solar wind
concentration, and speed; average IMF orientation has grown
somewhat less propitious for causing geomagnetic
activity. The combination of these factors explains almost
all of the 39\% rise in {\it aa} observed over the last
three solar cycles. Whereas the IMF strength varies
approximately in phase with sunspot numbers, neither its
orientation nor the solar wind density shows any coherent
solar cycle variation. The solar wind speed peaks strongly
in the declining phase of even-numbered cycles and can be
identified as the chief cause of the phase shift between the
sunspot numbers and the {\it aa} index. The rise in the IMF
magnitude, the largest single contributor to the drift in
geomagnetic activity, is shown to be caused by a rise in the
solar coronal magnetic field, consistent with a rise in the
coronal source field, modeled from photospheric
observations, and an observed decay in cosmic ray fluxes.}
}
@incollection{stamper97:_on_line_direc_groun_based_stp_obser,
author = {Stamper, R. and Wild, M. and Lockwood, M.},
editor = {Lockwood, M. and Wild, M.N. and Opgenoorth, H.J.},
title = {An On-Line Directory of Ground-Based STP Observatories},
booktitle = {Satellite - Ground Based Coordination Sourcebook},
pages = {367--407},
year = {1997},
publisher = {ESA},
volume = {SP-1198},
ukssdc_d = {},
ukssdc_w = {},
uk_first = {}
}
@article{stanislawska2001:_generation,
author = {Stanislawska, I. and Juchnikowski, G. and Zbyszynski, Z},
title = {Generation of instantaneous, maps of ionospheric
characteristics},
journal = {Radio Science},
year = {2001},
volume = {36},
number = {5},
pages = {1073--1081},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/1999RS002289},
abstract = {A way of producing limited-area instantaneous maps of
ionospheric characteristics is shown. An interpolation
technique is applied for construction of the mapping
model. The model combines monthly median maps of ionospheric
characteristics and a set of measurements for a single
moment of time that are exactly replicated during the
mapping procedure. The accuracy of the mapping results is
discussed, and samples of maps for different geophysical
conditions for $f_{o}F_{2}$, $f_{o}F_{1}$, $f_{o}E$ and
$M(3000)F_{2}$ are presented.}
}
@article{stanislawska2001:_forecasting,
author = {Stanislawska, I. and Zbyszynski, Z.},
title = {Forecasting of the ionospheric quiet and disturbed f(o)F(2)
values at a single location},
journal = {Radio Science},
year = {2001},
volume = {36},
number = {5},
pages = {1065--1071},
ukssdc_d = {},
ukssdc_i = {},
url = {http://dx.doi.org/10.1029/1999RS002242},
abstract = {The autocovariance prediction method has been used for
ionospheric forecasting of $f_{o}F_{2}$ values for 1, 2, 4,
8, and 12 hours ahead at a single location. Time series of
$f_{o}F_{2}$ data for ionospheric quiet and disturbed
conditions for February 1986 and September and December 1990
at different European stations were studied in order to
clarify the forecasting capabilities of the method for
ionospheric purposes. The accuracy of the method varies
within reasonable limits depending on the time range of the
forecast for different conditions. Samples of the results
for representative periods are presented. The forecast is
compared with observations, monthly median recommendations
of the Radiocommunication Sector of the International
Telecommunication Union (ITU-R), and persistence models.}
}
@article{stubbs04:_exten_polar,
author = {Stubbs, T.J. and Cargill, P.J. and Lockwood, M. and Grande,
M. and Kellett, B.J. and Perry, C.H.},
title = {Extended cusp-like regions and their dependence on the Polar
orbit, seasonal variations, and interplanetary conditions},
journal = {Journal of Geophysical Research},
year = 2004,
volume = 109,
number = {A09210},
url = {http://dx.doi.org/10.1029/2003JA010163},
ukssdc_d = {},
uk_first = {},
abstract = {Extended cusp-like regions (ECRs) are surveyed, as observed
by the Magnetospheric Ion Composition Sensor (MICS) of the
Charge and Mass Magnetospheric Ion Composition Experiment
(CAMMICE) instrument aboard Polar between 1996 and 1999. The
first of these ECR events was observed on 29 May 1996, an
event widely discussed in the literature and initially
thought to be caused by tail lobe reconnection due to the
coinciding prolonged interval of strong northward IMF. ECRs
are characterized here by intense fluxes of
magnetosheath-like ions in the energy-per-charge range of
$\sim1$ to 10 keV $e^{-1}$. We investigate the concurrence
of ECRs with intervals of prolonged (lasting longer than 1
and 3 hours) orientations of the IMF vector and high solar
wind dynamic pressure ($P_{SW}$). Also investigated is the
opposite concurrence, i.e., of the IMF and high $P_{SW}$
with ECRs. (Note that these surveys are asking distinctly
different questions.) The former survey indicates that ECRs
have no overall preference for any orientation of the
IMF. However, the latter survey reveals that during
northward IMF, particularly when accompanied by high
$P_{SW}$, ECRs are more likely. We also test for orbital and
seasonal effects revealing that Polar has to be in a
particular region to observe ECRs and that they occur more
frequently around late spring. These results indicate that
ECRs have three distinct causes and so can relate to
extended intervals in (1) the cusp on open field lines, (2)
the magnetosheath, and (3) the magnetopause indentation at
the cusp, with the latter allowing magnetosheath plasma to
approach close to the Earth without entering the
magnetosphere.}
}
@article{2006JGRA..11109110S,
author = {Svalgaard, L. and Cliver, E.W.},
title = {{Reply to the comment by M. Lockwood et al. on ``The IDV
index: Its derivation and use in inferring long-term
variations of the interplanetary magnetic field''}},
journal = {Journal of Geophysical Research (Space Physics)},
year = 2006,
month = sep,
volume = 111,
number = {A10},
pages = {9110-+},
doi = {10.1029/2006JA011678},
adsurl = {http://adsabs.harvard.edu/abs/2006JGRA..11109110S},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
ukssdc_d = {},
ukssdc_i = {}
}
@article{sykora03,
author = {Sykora, J. and Badalyan, O. G. and Obridko, V. N.},
title = {Connections between the white-light eclipse corona and
magnetic fields over the solar cycle},
journal = {Solar Physics},
pages = {301-318},
year = {2003},
month = {feb},
volume = {212},
number = {2},
url = {http://helios.izmiran.troitsk.ru/hellab/Obridko/17474496.pdf},
abstract = {Observations of ten solar eclipses (1973 1999) enabled us to
reveal and describe mutual relations between the white-light
corona structures (e.g., global coronal forms and most
conspicuous coronal features, such as helmet streamers and
coronal holes) and the coronal magnetic field strength and
topology. The magnetic field strength and topology were
extrapolated from the photospheric data under the
current-free assumption. In spite of this simplification the
found correspondence between the white-light corona
structure and magnetic field organization strongly suggests
a governing role of the field in the appearance and
evolution of local and global structures. Our analysis shows
that the study of white-light corona structures over a long
period of time can provide valuable information on the
magnetic field cyclic variations. This is particularly
important for the epoch when the corresponding measurements
of the photospheric magnetic field are absent.},
ukssdc_d = {}
}
@article{szuszczewicz1997,
author = {Szuszczewicz, E.P. and Blanchard, P. and Wilkinson, P. and
Crowley, G. and Fuller-Rowell, T. and Richards, P. and Abdu,
M. and Bullett, T. and Hanbaba, R. and Lebreton, J.P. and
Lester, M. and Lockwood, M. and Millward, G. and Wild,
M. and Pulinets, S. and Reddy, B.M. and Stanislawska, I. and
Vannaroni, G. and Zolesi, B.},
title = {The First Realtime Worldwide Ionospheric Prediction Network:
An Advance in Support of Spaceborne Experimentation, On-Line
Model Validation, and Space Weather},
journal = {Geophysical Research Letters},
pages = {449-452},
year = {1998},
month = {feb},
volume = {25},
number = {4},
abstract = {We report on the first realtime ionospheric predictions
network and its capabilities to ingest a global database and
forecast F-layer characteristics and ``in situ'' electron
densities along the track of an orbiting spacecraft. A
global network of ionosonde stations reported
around-the-clock observations of F-region heights and
densities, and an on-line library of models provided
forecasting capabilities. Each model was tested against the
incoming data; relative accuracies were intercompared to
determine the best overall fit to the prevailing conditions;
and the best-fit model was used to predict ionospheric
conditions on an orbit-to-orbit basis for the 12-hour period
following a twice-daily model test and validation
procedure. It was found that the best-fit model often
provided averaged (i.e., climatologically-based) accuracies
better than 5\% in predicting the heights and critical
frequencies of the F-region peaks in the latitudinal domain
of the TSS-1R flight path. There was a sharp contrast,
however, in model-measurement comparisons involving
predictions of actual, unaveraged, along-track densities at
the 295 km orbital altitude of TSS-1R. In this case, extrema
in the first-principle models varied by as much as an order
of magnitude in density predictions, and the best-fit models
were found to disagree with the ``in situ'' observations of
Ne by as much as 140\%. The discrepancies are interpreted as
a manifestation of difficulties in accurately and
self-consistently modeling the external controls of solar
and magnetospheric inputs and the spatial and temporal
variabilities in electric fields, thermospheric winds,
plasmaspheric fluxes, and chemistry.},
ukssdc_w = {},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{szuszczewicz92:_model,
author = {Szuszczewicz, E.P. and Fejer, B. and Roelof, E. and Schunk,
R. and Wolf, R. and Abdu, M. and Bateman, T. and Blanchard,
P. and Emery, B.A. and Feldstein, A. and Hanbaba, R. and
Joselyn, J. and Kikuchi, T. and Leitinger, R. and Lester,
M. and Sobral, J. and Reddy, B.M. and Richmond, A.D. and
Sica, R. and Walker, G.O. and Wilkinson, P.J.},
title = {Modelling and measurement of global-scale ionospheric
behaviour under solar minimum, equinoctial conditions},
journal = {Advances in Space Research},
pages = {105-115},
year = {1992},
month = {jan},
volume = {12},
number = {6},
abstract = {The global-scale modeling and measurement activities of the
Sundial campaign of September 1986 are examined, and
averaged, quiet-time, and dynamic ionospheric behaviors are
investigated. Treatment is given to developments in
empirical and first-principle models; and various aspects of
magnetospheric-thermospheric-ionospheric coupling mechanisms
are investigated. Overall results point to good empirical
model specification of averaged F-region behavior, with
suggestions for improvements in specification of layer peak
densities near and across the sunset terminator. The
difficulties in achieving a unique determination of electric
fields, thermospheric winds, and plasmaspheric fluxes are
elucidated in first-principle model attempts to reproduce
global observations of quiet-time F-region heights and
densities. In this connection, and in the treatment of
magnetospherically-imposed electric field influences on
low-latitude F-region dynamics, a greater need is shown for
comprehensive measurements of auroral oval dynamics,
thermospheric winds, electric fields, ion composition, and
ionospheric layer heights and densities. The growing
importance of the lower regions of the ionosphere and
thermosphere and the associated controls of dynamo-driven
electric fields are discussed.},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{szuszczewicz88:_sundial,
author = {Szuszczewicz, E.P. and Fejer, B. and Roelof, E. and Schunk,
R. and Wolf, R. and Leitinger, R. and Abdu, M. and Reddy,
B.M. and Joselyn, J. and Wilkinson, P.J. and Woodman, R.},
title = {SUNDIAL: a world-wide study of interactive ionospheric
processes and their roles in the transfer of energy and mass
in the Sun-Earth system},
journal = {Annales Geophysicae},
pages = {3-18},
year = {1988},
month = {feb},
volume = {6},
abstract = {Solar-terrestrial observations have been obtained in the
SUNDIAL program during the October 5-13, 1984 period in
order to explore cause and effect relationships controlling
the global-scale ionosphere. It is suggested that the
increased solar wind velocities noted are the result of a
corotating high-speed stream coupled to a transequatorial
solar coronal hole. The results are consistent with a
step-wise coupling of processes from the coronal hole
through the interplanetary and magnetospheric domains down
to the equatorial ionosphere, where penetrating electric
fields help trigger the most disturbed condition of
equatorial spread-F.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{szuszczewicz98,
author = {Szuszczewicz, E.P. and Lester, M. and Wilkinson, P. and
Blanchard, P. and Abdu, M. and Hanbaba, R. and Igarashi,
K. and Pulinets, S. and Reddy, B.M.},
title = {A comparative study of global ionospheric responses to
intense magnetic storm conditions},
journal = {Journal of Geophysical Research},
pages = {11665-11684},
year = {1998},
month = {jun},
volume = {103},
number = {A6},
abstract = {We report on a study of three intense ionospheric storms
that occurred in September 1989. Using Dst as a reference
for storm onset and subsequent main and recovery phases, we
analyze the observed worldwide responses of F region heights
hmF2 and densities NmF2 as a function of universal and local
times, latitudinal domains, and storm onset-times; and we
compare the characteristics of all three storms. The
following points are among the major findings: (1) The
negative phase storm was the dominant characteristic, with
the greatest intensity occurring in the regions which were
in the nighttime hemisphere during the main phase; (2) at
middle and low latitudes negative phase characteristics were
observed first in the nighttime hemisphere and then
corotated with the Earth into the dayside; (3) the most
intense negative response occurred in the recovery phase;
(4) observations of the negative phase characteristics
supported thermospheric upwelling, increased mean molecular
mass, and an associated enhancement in dissociative
recombination as the principal cause-effect chain; but the
observations suggest greater ion-neutral chemistry effects
than accounted for in current models; (5) hmF2 was observed
to respond quickly to the storm onset (pointing to the
importance of electric fields) with enhanced values in all
latitudinal and local time domains; (6) positive storm
characteristics were among the issues most difficult to
reconcile with current descriptions of cause-effect
relationships; and (7) the analysis of all storm phases and
comparisons with several modeling efforts show that future
advances in understanding require a more accurate accounting
of the influences of magnetospherically-imposed and
dynamo-driven electric fields, plasmaspheric fluxes, and
vibrationally excited $N_{2}$.},
ukssdc_d = {},
uk_other = {}
}
@article{szuszczewicz90:_solar_sundial,
author = {Szuszczewicz, E.P. and Wilkinson, P.J. and Abdu, M.A. and
Roelof, E. and Hanbaba, R. and Sands, M. and Kikuchi, T. and
Joselyn, J. and Burnside, R. and Lester, M. and Leitinger,
R. and Walker, G.O. and Reddy, B.M. and Sobral, J.},
title = {Solar-terrestrial conditions during Sundial-86 and empirical
modelling of the global-scale ionospheric response},
journal = {Annales Geophysicae},
pages = {387-398},
year = {1990},
month = {jun},
volume = {8},
abstract = {Covering the period from September 22 through October 4,
1986, the Sundial-86 Solar-Minimum Equinoctial Campaign
studied the behavior of the global-scale ionosphere. The
period covered the most quiet (Q1) and second most disturbed
(D2) days of the entire month of September, with the
disturbed conditions triggered by a high-speed solar wind
stream. Ionospheric responses were monitored by the Sundial
network of nearly 70 stations distributed approximately in
three longitudinal domains; and global maps of f0F2 results
were compared with the 'predictions' of the International
Reference Ionosphere modified to include an empirical
specification of auroral oval boundaries and associated
high-latitude morphological domains. Comparisons that
included regions in the polar cap, diffuse auroral oval,
mid-latitude trough, equatorial anomaly, and the
sunrise/sunset terminator showed good agreement between the
hourly 8-day-averaged ionospheric observations and the
model.},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{szuszczewicz93:_measur_f_sundial,
author = {Szuszczewicz, E.P. and Wilkinson, P.J. and Swider, W. and
Pulinets, S. and Abdu, M.A. and Roelof, E. and
Fuller-Rowell, T. and Evans, D.S. and Bateman, T. and
Blanchard, P. and Gustafsson, G. and Hanbaba, R. and
Joselyn, J. and Kikuchi, T. and Leitinger, R. and Lester,
M. and Reddy, B.M. and Ruohoniemi, M. and Sands, M. and
Sobral, J. and Walker, G.O. and Wickwar, V.},
title = {Measurements and empirical model comparisons of F-region
characteristics and auroral oval boundaries during the
solstitial SUNDIAL campaign of 1987},
journal = {Annales Geophysicae},
pages = {601},
year = {1993},
volume = {11},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {}
}
@article{taylor1994,
author = {Taylor, J.R. and Lester M. and Yeoman, T.K.},
title = {A superposed epoch analysis of geomagnetic storms},
url = {http://www.springerlink.com/content/um663257371w0043/},
pdf = {http://www.springerlink.com/content/um663257371w0043/fulltext.pdf},
journal = {Annales Geophysicae},
pages = {612--624},
year = {1994},
volume = {12},
number = {7},
abstract = {A superposed epoch analysis of geomagnetic storms has been
undertaken. The storms are categorised via their intensity
(as defined by the Dst index). Storms have also been
classified here as either storm sudden commencements (SSCs)
or storm gradual commencements (SGCs, that is all storms
which did not begin with a sudden commencement). The
prevailing solar wind conditions defined by the parameters
solar wind speed ($v_{sw}$), density ($\rho_{sw}$) and
pressure ($P_{sw}$) and the total field and the components
of the interplanetary magnetic field (IMF) during the storms
in each category have been investigated by a superposed
epoch analysis. The southward component of the IMF, appears
to be the controlling parameter for the generation of small
SGCs (-100 nT< minimum Dst $\leq$ -50 nT for $\geq$ 4 h),
but for SSCs of the same intensity solar wind pressure is
dominant. However, for large SSCs (minimum Dst $\leq$ -100
nT for $\geq$ 4 h) the solar wind speed is the controlling
parameter. It is also demonstrated that for larger storms
magnetic activity is not solely driven by the accumulation
of substorm activity, but substantial energy is directly
input via the dayside. Furthermore, there is evidence that
SSCs are caused by the passage of a coronal mass ejection,
whereas SGCs result from the passage of a high speed/slow
speed coronal stream interface. Storms are also grouped by
the sign of $B_{z}$ during the first hour epoch after the
onset. The sign of $B_{z}$ at t=+1 h is the dominant sign of
the $B_{z}$ for $\sim$24 h before the onset. The total
energy released during storms for which $B_{z}$ was
initially positive is, however, of the same order as for
storms where $B_{z}$ was initially negative.},
ukssdc_d = {},
uk_first = {}
}
@article{tsagouri2005,
author = {Tsagouri, I. and Zolesi, B. and Belehaki, A. and Cander,
Lj.},
title = {Evaluation of the performance of the real-time updated
simplified ionospheric regional model for the European area},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
volume = {67},
number = {12},
pages = {1137--1146},
year = {2005},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
abstract = {The increasing demand for upper-atmosphere nowcasting
services for operational applications reveals the need for a
realistic mapping of the ionosphere over Europe in real-time
and especially during storm periods. To meet this need, a
real-time updating method of simplified ionospheric regional
model (SIRM) with autoscaled ionospheric characteristics
observed by four European Digital Portable Sounders (DPS)
ionosondes was recently developed. SIRM belongs to the group
of ionospheric models for the standard vertical incidence
(VI) ionospheric characteristics such as the critical
frequency of the ionospheric F2 layer foF2 and the
propagation factor M(3000)F2, which oversimplify a number of
the ionospheric phenomena of real significance for radio
communications applications showing satisfactory performance
for median ionospheric condition description in restricted
area of mid-latitudes. As a step forward, the rapid
conversion of real-time data from four European digisondes
to the driving parameters of the SIRM was introduced as the
real-time SIRM updating (SIRMUP). In SIRMUP approach, the
values of the ionospheric characteristics from first-guess
model parameters at measurement points are combined with
real-time measurements. The reliability of the real-time
SIRM update method has already been tested in terms of the
foF2 for various ionospheric conditions and the simulation
results were very promising. In this paper, the simulation
tests are continued in order to investigate the efficiency
of the SIRMUP method in mapping the propagation conditions
over Europe as they are expressed by the propagation factor
M(3000)F2. In general, the results demonstrate that SIRMUP
procedure has the potential to be used in real time for
nowcasting the standard ionospheric characteristics over
Europe, for operational applications.},
keywords = {Ionospheric radio-propagation; Ionospheric mapping;
Ionospheric modelling; Mid-latitude ionosphere},
url = {http://dx.doi.org/10.1016/j.jastp.2005.01.012}
}
@article{tulunay00:_tempor,
author = {Tulunay, E. and \"{O}zkaptan, C. and Tulunay, Y.K.},
title = {Temporal and spatial forecasting of the foF2 values up to
twenty four hour in advance},
journal = {Physics and Chemistry of the Earth},
pages = {281--285},
year = {2000},
month = mar,
volume = {25},
number = {4},
ukssdc_d = {}
}
@article{tulunay1997:poss_eff_IMF_COST,
author = {Tulunay, Y. and Kaya, A. and Kaymaz, Z.},
title = {The Possible Effect of the IMF By and Bz Components on the
High Latitude COST 251 Area},
journal = {Advances in Space Research},
pages = {1723--1726},
year = {1997},
volume = {20},
number = {9},
abstract = {The possible effects of the orientation of the IMF on the
ionosphere has been studied by Tulunay (1995) using foF2
data from 15 ionospheric stations in Europe over the COST
238 area. The results showed that a good amount of the day
to day variability of the mid-latitude ionospheric F region
could be related to changes in orientation of the southward
IMF Bz. This variability is quantified as the maximum change
of deltafoF2. This paper investigates the effects of By
distribution on the ionospheric critical frequencies.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{tulunay96:_inter_magnet_field_imf,
author = {Tulunay, Y.K.},
title = {Interplanetary Magnetic Field (IMF) and its possible effects
on the mid-latitude ionosphere:III},
journal = {Annali di Geofisica},
pages = {853--862},
year = {1996},
abstract = {Using critical frequencies, f0F2 from the Lannion, Slough,
Poitiers, Garchy, Dourbes, Rome, Juliusrud, Gibilmanna,
Pruhonice, Uppsala, Kaliningrad, Miedzeszyn, Sofia, Athens
and Kiev ionosonde stations, the possible effects of the
orientation of the Interplanetary Magnetic Field (IMF) on
mid-latitude ionosphere are further investigated. This time,
only the southward polarity changes in IMF Bz with seasonal
effects were considered. The same method of analysis was
employed to facilitate a comparison between the recent
results presented here with those which appeared in the
preceding papers in the series. That is, the regular
diurnal, seasonal and solar cycle variations in the f0F2
data were removed by subtracting the mean of the f0F2 for
the same UT on all magnetically quite days (Ap < 6) within
15 days around the IMF Bz turnings (Tulunay, 1994). This
last paper also includes the seasonal effects on the
ionospheric data. The results confirm that much of the
day-to-day variability of the mid-latitude ionosphere may be
related to the orientation of the southward IMF Bz ,
characterized by the ionospheric winter anomaly. Day-to-day
ionospheric variability becomes more significant towards
higher latitudes.},
ukssdc_d = {}
}
@article{variabilit:1995,
author = {Tulunay, Y.K.},
title = {Variability of mid-latitude ionospheric foF2 compared to IMF
polarity inversions},
journal = {Advances in Space Research},
pages = {35--44},
year = {1995},
volume = {15},
number = {2},
abstract = {Potential effects of the IMF-orientation on the mid-latitude
ionosphere are further investigated using critical
frequencies foF2 from six ionosonde stations. For a period
of 15 days around each inversion of BZ, excluding all days
with Ap >=6, a quiet standard diurnal variation was
determined by day-by-day averaging for each hour UT. The
regular diurnal, seasonal and solar cycle variations were
then removed from the data by substracting from these the
quiet standard value. The so obtained differences foF2 were
sorted after the IMF polarity. Distinct effects of northward
and southward inversions were found so that a large part of
the day-to day variability may be attributed to IMF BZ
polarity changes. },
ukssdc_d = {},
ukssdc_i = {}
}
@article{villante04,
author = {Villante, U. and Di Giuseppe, P.},
title = {Some aspects of the geomagnetic response to solar wind
pressure variations: a case study at low and middle
latitudes},
journal = {Annales Geophysicae},
pages = {2053-2066},
year = {2004},
volume = {22},
number = {6},
abstract = {We examined geomagnetic field observations at low and middle
latitudes in the Northern Hemisphere during a 50-min
interval (12 May 1999), characterized by a complex behaviour
of the solar wind dynamic pressure. For the entire interval,
the aspects of the geomagnetic response can be organized
into four groups of events which show common characteristics
for the H and D components, respectively. The correspondence
between the magnetospheric field and the ground components
reveals different aspects of the geomagnetic response in
different magnetic local time (MLT) sectors. For the H
component, the correspondence is highly significant in the
dusk and night sectors; in the dawn and prenoon sectors it
shows a dramatic change across a separation line that
extends approximately between (6 MLT, $35^{\circ}$) and (13
MLT, $60^{\circ}$). For the D component, the correspondence
has significant values in the dawn and prenoon regions. We
propose a new approach to the experimental data analysis
which reveals that, at each station, the magnetospheric
field has a close correspondence with the geomagnetic field
projection along an axis (M1) that progressively rotates
from north/south (night events) to east/west orientation
(dawn events). When projected along M1, the geomagnetic
signals can be interpreted in terms of a one-dimensional
pattern that mostly reflects the field behaviour observed at
geostationary orbit. Several features appear more evident in
this perspective, and the global geomagnetic response to the
SW pressure variations appears much clearer than in other
representations. In particular, the MLT dependence of the
geomagnetic response is much smaller than that one estimated
by previous investigations. A clear latitudinal dependence
emerges in the dusk sector. The occurrence of low frequency
waves at $\sim2.8$mHz can be interpreted in terms of global
magnetospheric modes driven by the SW pulse. This event
occurred in the recovery phase after the day the SW almost
disappeared (11 May 1999): in this sense our results suggest
a rapid recovery of almost typical magnetospheric conditions
soon after a huge expansion. Overshoot amplitudes, greater
than in other cases, are consistent with a significant
reduction of the ring current.},
ukssdc_d = {}
}
@article{2006AnGeo..24..887V,
author = {Voiculescu, M. and Aikio, A.T. and Nygr{\'e}n, T. and
Ruohoniemi, J.M.},
title = {{IMF effect on sporadic-E layers at two northern polar cap
sites: Part I Statistical study}},
journal = {Annales Geophysicae},
year = 2006,
month = may,
volume = 24,
pages = {887-900},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24..887V},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {n this paper we investigate the relationship between polar
cap sporadic-E layers and the direction of the
interplanetary magnetic field (IMF) using a 2-year database
from Longyearbyen (75.2 CGM Lat, Svalbard) and Thule (85.4
CGM Lat, Greenland). It is found that the MLT distributions
of sporadic-E occurrence are different at the two stations,
but both are related to the IMF orientation. This
relationship, however, changes from the centre of the polar
cap to its border. Layers are more frequent during positive
By at both stations. This effect is particularly strong in
the central polar cap at Thule, where a weak effect
associated with Bz is also observed, with positive Bz
correlating with a higher occurrence of Es. Close to the
polar cap boundary, at Longyearbyen, the By effect is weaker
than at Thule. On the other hand, Bz plays there an equally
important role as By, with negative Bz correlating with the
Es occurrence. Since Es layers can be created by electric
fields at high latitudes, a possible explanation for the
observations is that the layers are produced by the polar
cap electric field controlled by the IMF. Using electric
field estimates calculated by means of the statistical APL
convection model from IMF observations, we find that the
diurnal distributions of sporadic-E occurrence can generally
be explained in terms of the electric field
mechanism. However, other factors must be considered to
explain why more layers occur during positive than during
negative By and why the Bz dependence of layer occurrence in
the central polar cap is different from that at the polar
cap boundary.},
ukssdc_d = {},
ukssdc_i = {}
}
@article{walden08:_extraordinary_wave,
user = {mcw@plextek.co.uk},
author = {Walden, M.C.},
title = {Extraordinary Wave NVIS Propagation at 5 MHz},
journal = {Radio Communications - Journal of the Radio Society of Great Britain},
volume = {84},
number = {03},
pages = {57-62},
year = {2008},
month = mar,
ukssdc_d = {},
uk_other = {},
abstract = {}
}
@article{watkins00:_ambig_deter_self_affin_ae,
author = {Watkins, N.W. and Freeman, M.P. and Rhodes, C.S. and
Rowlands, G.},
title = {Ambiguities in Determination of Self-Affinity in the
AE-Index Time Series},
journal = {Fractals-complex geometry patterns and scaling in nature and
society},
pages = {471-479},
year = {2001},
month = {nov},
volume = {9},
number = {4},
abstract = {The interaction between the Earth's magnetic field and the
solar wind plasma results in a natural plasma confinement
system which stores energy. Dissipation of this energy
through Joule heating in the ionosphere can be studied via
the Auroral Electrojet (AE) index. The apparent broken power
law form of the frequency spectrum of this index has
motivated investigation of whether it can be described as
fractal coloured noise. One frequently-applied test for
self-affinity is to demonstrate linear scaling of the
logarithm of the structure function of a time series with
the logarithm of the dilation factor $\lambda$. We point out
that, while this is conclusive when applied to signals that
are self-affine over many decades in $\lambda$, such as
Brownian motion, the slope deviates from exact linearity and
the conclusions become ambiguous when the test is used over
shorter ranges of $\lambda$. We demonstrate that non
self-affine time series made up of random pulses can show
near-linear scaling over a finite dynamic range such that
they could be misinterpreted as being self-affine. In
particular we show that pulses with functional forms such as
those identified by Weimer within the $AL$ index, from which
$AE$ is partly derived, will exhibit nearly linear scaling
over ranges similar to those previously shown for $AE$ and
$AL$. The value of the slope, related to the Hurst exponent
for a self-affine fractal, seems to be a more robust
discriminator for fractality, if other information is
available.},
ukssdc_d = {},
uk_first = {}
}
@article{willis1996,
author = {Willis, D.M. and Davda, V.N. and Stephenson, F.Richard},
title = {Comparison between Oriental and Occidental Sunspot
Observations},
journal = {Quarterly Journal of the Royal Astronomical Society},
pages = {189--229},
year = {1996},
month = {jun},
volume = {37},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{2006AnGeo..24.2743W,
author = {Willis, D.M. and Henwood, R. and Stephenson, F.R.},
title = {The presence of large sunspots near the central solar
meridian at the times of modern Japanese auroral
observations},
journal = {Annales Geophysicae},
year = 2006,
month = oct,
volume = 24,
pages = {2743-2758},
adsurl = {http://adsabs.harvard.edu/abs/2006AnGeo..24.2743W},
adsnote = {Provided by the Smithsonian/NASA Astrophysics Data System},
abstract = {The validity of a technique developed by the authors to
identify historical occurrences of intense geomagnetic
storms, which is based on finding approximately coincident
observations of sunspots and aurorae recorded in East Asian
histories, is corroborated using more modern sunspot and
auroral observations. Scientific observations of aurorae in
Japan during the interval 1957-2004 are used to identify
geomagnetic storms that are sufficiently intense to produce
auroral displays at low geomagnetic latitudes. By examining
white-light images of the Sun obtained by the Royal
Greenwich Observatory, the Big Bear Solar Observatory, the
Debrecen Heliophysical Observatory and the Solar and
Heliospheric Observatory spacecraft, it is found that a
sunspot large enough to be seen with the unaided eye by an
"experienced" observer was located reasonably close to the
central solar meridian immediately before all but one of the
30 distinct Japanese auroral events, which represents a 97\%
success rate. Even an "average" observer would probably
have been able to see a sunspot with the unaided eye before
24 of these 30 events, which represents an 80\% success
rate. This corroboration of the validity of the technique
used to identify historical occurences of intense
geomagnetic storms is important because early unaided-eye
observations of sunspots and aurorae provide the only
possible means of identifying individual historical
geomagnetic storms during the greater part of the past two
millennia.},
uk_first = {},
ukssdc_d = {},
ukssdc_i = {}
}
@article{willis09:_presen_of_large_sunsp_near,
author = {Willis, D.M. and Henwood, R. and Stephenson, F.R.},
title = {The presence of large sunspots near the central solar
meridian at the times of major geomagnetic storms},
journal = {Annales Geophysicae},
year = 2009,
volume = 27,
pages = {185--197},
number = {1},
url = {http://www.ann-geophys.net/27/185/2009/},
month = jan,
abstract = {A further study is made of the validity of a technique
developed by the authors to identify historical occurrences
of intense geomagnetic storms, which is based on finding
approximately coincident observations of sunspots and
aurorae recorded in East Asian histories. Previously, the
validity of this technique was corroborated using scientific
observations of aurorae in Japan during the interval
1957--2004 and contemporaneous white-light images of the Sun
obtained by the Royal Greenwich Observatory, the Big Bear
Solar Observatory, the Debrecen Heliophysical Observatory,
and the Solar and Heliospheric Observatory spacecraft. The
present investigation utilises a list of major geomagnetic
storms in the interval 1868--2008, which is based on the
magnitude of the AA* magnetic index, and reconstructed solar
images based on the sunspot observations acquired by the
Royal Greenwich Observatory during the shorter interval
1874--1976. It is found that a sunspot large enough to be
seen with the unaided eye by an "experienced" observer was
located reasonably close to the central solar meridian for
almost 90\% of these major geomagnetic storms. Even an
"average" observer would easily achieve a corresponding
success rate of 70\% and this success rate increases to
about 80\% if a minority of ambiguous situations are
interpreted favourably. The use of information on major
geomagnetic storms, rather than modern auroral observations
from Japan, provides a less direct corroboration of the
technique for identifying historical occurrences of intense
geomagnetic storms, if only because major geomagnetic storms
do not necessarily produce auroral displays over East
Asia. Nevertheless, the present study provides further
corroboration of the validity of the original technique for
identifying intense geomagnetic storms. This additional
corroboration of the original technique is important because
early unaided-eye observations of sunspots and aurorae
provide the only possible means of identifying individual
geomagnetic storms during the greater part of the past two
millennia.},
uk_first = {},
ukssdc_d = {},
ukssdc_w = {}
}
@article{willis07:_sporadic_aurorae,
user = {r.henwood@rl.ac.uk},
author = {Willis, D.M. and Stephenson, F. R. and Huiping Fang},
title = {Sporadic aurorae observed in East Asia},
journal = {Annales Geophysicae},
volume = {25},
number = {2},
pages = {417-436},
year = {2007},
month = mar,
url = {http://www.ann-geophys.net/25/417/2007/angeo-25-417-2007.html},
pdf = {http://www.ann-geophys.net/25/417/2007/angeo-25-417-2007.pdf},
ukssdc_w = {},
ukssdc_d = {},
abstract = {All the accessible auroral observations recorded in Chinese
and Japanese histories during the interval AD 1840--1911 are
investigated in detail. Most of these auroral records have
never been translated into a Western language before. The
East Asian auroral reports provide information on the date
and approximate location of each auroral observation,
together with limited scientific information on the
characteristics of the auroral luminosity such as colour,
duration, extent, position in the sky and approximate time
of occurrence. The full translations of the original Chinese
and Japanese auroral records are presented in an appendix,
which contains bibliographic details of the various
historical sources. (There are no known reliable Korean
observations during this interval.) A second appendix
discusses a few implausible "auroral" records, which have
been rejected. The salient scientific properties of all
exactly dated and reliable East Asian auroral observations
in the interval AD 1840--1911 are summarised succinctly. By
comparing the relevant scientific information on exactly
dated auroral observations with the lists of great
geomagnetic storms compiled by the Royal Greenwich
Observatory, and also the tabulated values of the Ak
(Helsinki) and aa (Greenwich and Melbourne) magnetic
indices, it is found that 5 of the great geomagnetic storms
(aa>150 or Ak>50) during either the second half of the
nineteenth century or the first decade of the twentieth
century are clearly identified by extensive auroral displays
observed in China or Japan. Indeed, two of these great
storms produced auroral displays observed in both countries
on the same night. Conversely, at least 29 (69\%) of the 42
Chinese and Japanese auroral observations occurred at times
of weak-to-moderate geomagnetic activity (aa or
Ak$\leq$50). It is shown that these latter auroral displays
are very similar to the more numerous (about 50) examples of
sporadic aurorae observed in the United States during the
interval AD 1880--1940. The localised nature and spatial
structure of some sporadic aurorae observed in East Asia is
indicated by the use of descriptive terms such as
"lightning", "rainbow", "streak" and "grid".}
}
@article{willis79:_statis,
author = {Willis, D.M. and Tulunay, Y.K.},
title = {Statistics of the largest sunspot and facular areas per
solar cycle},
journal = {Solar Physics},
pages = {237--246},
year = {1979},
volume = {64},
abstract = {The paper uses the statistics of extreme values to
investigate the statistical properties of the largest areas
of sunspots and photospheric faculae per solar cycle. The
largest values of the synodic-solar-rotation mean areas of
umbrae, whole spots and faculae, which have been recorded
for nine solar cycles are shown to comply with the general
form of the extreme value probability function. Empirical
expressions are derived for the three extreme value
populations from which the characteristic statistic
parameters, namely the mode, median, mean and standard
deviation, can be calculated for each population. It is
found that extreme areas of umbrae and whole spots have a
diversion comparable to that found by Siscoe for the extreme
values of sunspot number whereas the extreme areas of
faculae have a smaller dispersion which is comparable to
that found by Siscoe for the largest geomagnetic storm per
solar cycle.},
ukssdc_w = {},
ukssdc_d = {},
uk_first = {}
}
@article{wintoft2000,
author = {Wintoft, P. and Cander, L.R.},
title = {Twenty-four hour predictions of f(o)F(2) using time delay
neural networks},
journal = {Radio Science},
year = {2000},
volume = {35},
number = {2},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
abstract = {The use of time delay feed-forward neural networks to
predict the hourly values of the ionospheric F-2 layer
critical frequency, $f_{o}F_{2}$, 24 hours ahead, have been
examined. The 24 measurements of $f_{o}F_{2}$ per day are
reduced to five coefficients with principal component
analysis. A time delay line of these coefficients is then
used as input to a feed-forward neural network. Also
included in the input are the 10.7 cm solar flux and the
geomagnetic index Ap. The network is trained to predict
measured $f_{o}F_{2}$ data from 1965 to 1985 at Slough
ionospheric station and validated on an independent
validation set from the same station for the periods
1987-1990 and 1992-1994. The results are compared with two
different autocorrelation methods for the years 1986 and
1991, which correspond to low and high solar activity,
respectively.},
keywords = {SOLAR-WIND DATA; GEOMAGNETIC STORMS},
url = {http://dx.doi.org/10.1029/1998RS002149}
}
@article{wu95:_time_weigh,
author = {Wu, J.P. and Wilkinson, P.J.},
title = {Time Weighted magnetic indices as predictors of ionospheric
behaviour},
url = {http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VSV-40SFK5G-6&_user=910841&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000047841&_version=1&_urlVersion=0&_userid=910841&md5=3a3ad475fed4023099d855250a27e728},
journal = {Journal of Atmospheric and Terrestrial Physics},
pdf = {http://www.sciencedirect.com/science?_ob=MImg&_imagekey=B6VSV-40SFK5G-6-1&_cdi=6272&_user=910841&_orig=search&_coverDate=12%2F31%2F1995&_sk=999429985&view=c&chp=dGLbVtz-zSkzS&md5=f456581f0dead0a40277cd85da050a98&ie=/sdarticle.pdf},
pages = {1763--1770},
year = {1995},
volume = {57},
number = {14},
abstract = {A time-weighted accumulation of the ap index, ap($\tau$)
(Wrenn, 1987; Wrenn et al., 1987, 1989), together with other
similar indices, was explored as a predictor of ionospheric
behaviour, using $f_{o}F_{2}$ data for a selection of
locations in Australia and Europe for September and October
1989. All the time accumulated indices showed improved
linear correlations, indicative of a response time of the
order of about 15 hours. The response time could be
decomposed into a lag between respective time series and a
persistence time, although the decomposition appeared
unnecessary as the persistence time carried the same
information. Of the individual indices investigated, {\it
aa}($\tau$) appeared best and the auroral oval equatorward
edge index (AI index) was poorest, although the differences
were not statistically significant. Comparisons between the
{\it aa}, ap and Kp indices, plus comparisons between
different ionospheric parameters showed that forecasting may
be improved using different transformations of the
data. While these results appear good, further studies using
other stations and seasons are warranted to confirm their
utility for forecasting. },
ukssdc_d = {},
ukssdc_i = {}
}
@article{yu04,
author = {Yu, T. and Wan, W. and Liu, L. and Zhao, B.},
title = {Global scale annual and semi-annual variations of daytime
NmF2 in the high solar activity years},
journal = {Journal of Atmospheric and Solar-Terrestrial Physics},
pages = {1691-1701},
year = {2004},
month = {dec},
volume = {66},
number = {18},
abstract = {The annual and semi-annual variations of the ionosphere are
investigated in the present paper by using the daytime F2
layer peak electron concentration (NmF2) observed at a
global ionosonde network with 104 stations. The main
features are outlined as follows. (1) The annual variations
are most pronounced at magnetic latitudes of $40-60^{\circ}$
in both hemispheres, and usually manifest as winter
anomalies; Below magnetic latitude of $40^{\circ}$ as well
as in the tropical region they are much weaker and winter
anomalies that are not obvious. (2) The semi-annual
variations, which are usually peak in March or April in most
regions, are generally weak in the near-pole regions and
strong in the far-pole regions of both hemispheres. (3)
Compared with their annual components, the semi-annual
variations in the tropical region are more significant. In
order to explain the above results, we particularly analyze
the global atomic/molecular ratio of [O/N$_{2}$] at the F2
layer peak height by the MSIS90 model. The results show that
the annual variation of [O/N$_{2}$] is closely related with
that of NmF2 prevailing in mid-latitudes and [O/N$_{2}$]
annual variation usually may lead to the winter anomalies of
NmF2 occurring in the near-pole region. Moreover, NmF2
semi-annual variations appearing in the tropical region also
have a close relationship with the variation of
[O/N$_{2}$]. On the other hand, the semi-annual variations
of NmF2 in the far-pole region cannot be simply explained by
that of [O/N$_{2}$], but the variation of the solar zenith
angle may also have a significant contribution.},
ukssdc_d = {}
}
@article{zolesi04:_real-time,
author = {Zolesi, B. and Belahaki, A. and Tsagouri, I. and Cander,
L.R.},
title = {Real-time updating of the Simplified Ionospheric Regional
Model for operational applications},
journal = {Radio Science},
year = {2004},
volume = {39},
number = {2},
ukssdc_d = {},
ukssdc_i = {},
uk_other = {},
url = {http://dx.doi.org/10.1029/2003RS002936},
abstract = {A method for mapping of ionospheric conditions over Europe,
suitable to be used in real time for operational
applications, is described in this paper. The method is
based on the Simplified Ionospheric Regional Model ( SIRM),
a regional model of the standard vertical incidence monthly
median ionospheric characteristics that has been updated
with real-time ( automatic scaled) ionospheric observations
to produce nowcasting maps over Europe. As substantial
fluctuations from a monthly median regional ionospheric
description occur on day-to-day basis, the SIRM results
oversimplified a number of the ionospheric phenomena of real
significance for radio communications
applications. Therefore a rapid conversion of real-time data
from four European digisondes ( Digital Portable Sounders)
to the driving parameters of the Simplified Ionospheric
Regional Model is introduced as the real-time SIRM updating
(SIRMUP). In this approach, values of the ionospheric
characteristics from first-guess model parameters at
measurement points are combined with real-time
measurements. To assess the qualitative improvements
achieved with the real-time SIRM update method, observations
of foF2 parameter with SIRMUP predictions were compared for
various ionospheric conditions. The simulation shows that
the SIRMUP prediction results are much improved comparing to
SIRM predictions, especially during large-scale ionospheric
disturbances, as well as during quiet conditions, while
there was a marginal improvement during localized
ionospheric disturbances. In general, the results clearly
demonstrate that the proposed procedure of updating SIRM
with automatic scaling ionospheric parameters from the four
European digisondes has the potential to be used in real
time for nowcasting the standard ionospheric characteristics
over Europe for operational applications.}
}
@article{zou00:_annual_f2,
author = {Zou, L. and Rishbeth, H. and Muller-Wodarg, I.C.F. and
Aylward, A.D. and Millward, G.H. and Fuller-Rowell, T.J. and
Idenden, D.W. and Moffett, R.J.},
title = {Annual and semiannual variations in the ionospheric
F2-layer. I. Modelling},
journal = {Annales Geophysicae},
pages = {927--944},
year = {2000},
volume = {18},
number = {8},
abstract = {Annual, seasonal and semiannual variations of F2-layer
electron density (NmF2) and height (hmF2) have been compared
with the coupled thermosphere-ionosphere-plasmasphere
computational model (CTIP), for geomagnetically quiet
conditions. Compared with results from ionosonde data from
midlatitudes, CTIP reproduces quite well many observed
features of NmF2, such as the dominant winter maxima at high
midlatitudes in longitude sectors near the magnetic poles,
the equinox maxima in sectors remote from the magnetic poles
and at lower latitudes generally, and the form of the
month-to-month variations at latitudes between about
$60^{\circ}$N and $50^{\circ}$S. CTIP also reproduces the
seasonal behaviour of NmF2 at midnight and the summer-winter
changes of hmF2. Some features of the F2-layer, not
reproduced by the present version of CTIP, are attributed to
processes not included in the modelling. Examples are the
increased prevalence of the winter maxima of noon NmF2 at
higher solar activity, which may be a consequence of the
increase of F2-layer loss rate in summer by vibrationally
excited molecular nitrogen, and the semiannual variation in
hmF2, which may be due to tidal effects. An unexpected
feature of the computed distributions of NmF2 is an
east-west hemisphere},
ukssdc_d = {},
ukssdc_i = {},
uk_first = {}
}
UK Solar System Data Centre