@COMMENT{{{This file has been generated by bib2bib 1.74}}
@COMMENT{{{Command line: /soft/ukssdc/share/bib2bib -c 'exists ukssdc_d' -c 'year = 2005 or year = 2006 or year = 2007' -s author -ob ukssdc_d_20052007.bib ukssdc.bib}}
@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 degrees 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 Kp <= 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 (Kp
<= 2(+)) and disturbed (Kp > 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{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{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{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. (c) 2005 Elsevier Ltd. All rights reserved.}
}
@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{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 F 2-layer expressed by the maximum
critical frequency foF 2. Similar indices derived from ionospheric M(3000)F
2 values show a markedly lower variability indicating that the changes of
the altitude of the F 2-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°N¿60°N; 5°W¿40°E)
can now be displayed online. },
UK_OTHER = {},
UKSSDC_D = {},
UKSSDC_I = {}
}
@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{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{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 = {}
}
@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 = {}
}
@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{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{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¿, 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{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{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{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 +/-18$\deg$ 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$\deg$ 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{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. (c) 2005 Elsevier Ltd. All rights reserved.}
}
@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{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{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{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{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{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-¿ 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 Enosin4($\theta$/2) and estimate the peak value, Eno, by matching
observed and modeled variations of both the latitude, ¿OCB, of the dayside
OCB (as inferred from the equatorward edge of cusp proton emissions seen by
FUV) and the transpolar voltage ¿PC (as derived using the mapped potential
technique from SuperDARN HF radar data). This analysis also yields the time
constant ¿OCB with which the open-closed boundary relaxes back toward its
equilibrium configuration. For the case studied here, we find ¿OCB = 9.7 +/-
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{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{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{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{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{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{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". (c) 2005 Elsevier Ltd. All rights
reserved.}
}
@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 F 2 layer f o F 2 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{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 35degreesN - 70degreesN and 5degreesW -
40degreesE. 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{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{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{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
+/- 4.5% between 1903 and 1956, associated with a 14.4 +/- 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 +/- 5.0%, but the best
procedure, giving the narrowest and most symmetric distribution of fit
residuals, yields 87.3 +/- 3.9%.},
UK_FIRST = {},
UKSSDC_D = {},
UKSSDC_I = {}
}
@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{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{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{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{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 = {}
}
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