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| Titel |
Use of GIMs in high and midlatitudes |
| VerfasserIn |
Elena Andreeva, Svetlana Kalashnikova, Viacheslav Kunitsyn, Evgeny Tereshchenko |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250056977
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| Zusammenfassung |
| The technology of global ionospheric maps (GIMs) is one of most prevailing methods of
ionospheric studies, which allows to estimate vertical total electron content (VTEC) almost
all over the Earth with the resolution of 5Ë of longitude and 2.5Ë of latitude and temporal
step of 2 h. The methods applied in the GIM construction at several data processing centers
are different although all based on the common idea of finding the appropriate model
parameters to fit the selected model of the vertical distribution of electron density
to the observed GPS data. To understand if GIMs may be similarly used in any
conditions we compared this method with the results of low-orbital radio tomography
(LORT) reconstructions along RT systems in Russia and Alaska during 2003-2007
years.
To find out more information about ionosphere we examined the results of UV-spectrometry
as a principally different method of VTEC’s estimation as far as night emissions of O+ ions,
generated by its reaction of radiative recombination with electrons, in first approximation, are
proportional to the integral of squared electron density. We studied the data of Global
Ultraviolet Imager (GUVI), which is one of four instruments constituting the TIMED
(Thermosphere Ionosphere Mesosphere Energetics and Dynamics) spacecraft. It is
a far-ultraviolet (115 to 180 nm), scanning imaging spectrograph that provides
horizon-to-horizon images in five selectable wavelength intervals, or “colors". These colors
(HI 121.6 nm, OI 130.4 nm, OI 135.6 nm, and N2 Lyman-Birge-Hopfield bands
140 to 150 nm and 165 to 180 nm) are chosen in order to produce the GUVI key
parameters.
The analysis shows that the resolution of GIMs, is not, at fact, as good as declared. Large
structures reaching the size of about 10Ë distinctly reconstructed by LORT and well seen in
GUVI data are often not observed in GIMs or have larger scales, especially during the periods
of strong geomagnetic activity. GIM vertical TEC is often much more smoothed, compared to
LORT data, and can’t represent all fast processes taking place in the ionosphere. The
reconstructions for quiet periods are basically similar, although higher GIM vertical TEC
values compared to LORT vertical TEC, which might be due to the plasmaspheric
contribution, are still noteworthy.
We are grateful to North West Research Associates for experimental TEC data in
Alaska region. GUVI data were obtained from http://guvi.jhuapl.edu/, GIM data from
ftp://cddis.gsfc.nasa.gov/pub/gps/products/ionex/ .
The work was supported by the Russian Foundation for Basic Research (grants nos.
10-05-01126, 11-05-01157) and Ministry of Science and Education of Russian Federation
(projects NK-56P/24 and 14.740.11.0203). |
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