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| Titel |
Climatology of zonal wind and large-scale FAC with respect to the density anomaly in the cusp region: seasonal, solar cycle, and IMF By dependence |
| VerfasserIn |
G. N. Kervalishvili, H. Lühr |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 32, no. 3 ; Nr. 32, no. 3 (2014-03-20), S.249-261 |
| Datensatznummer |
250121038
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| Publikation (Nr.) |
 copernicus.org/angeo-32-249-2014.pdf |
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| Zusammenfassung |
| We investigate the relationship of the thermospheric density anomaly
(ρrel) with the neutral zonal wind velocity (Uzonal),
large-scale field-aligned current (FAC), small-scale FAC, and electron
temperature (Te) using the superposed epoch analysis (SEA) method
in the cusp region. The dependence of these variables on the sign of the
interplanetary magnetic field (IMF) By component and local season is of
particular interest. Also, the conditions that lead to larger relative
density enhancements are investigated. Our results are based on CHAMP
satellite data and OMNI online data of IMF for solar maximum (March
2002–March 2007) and minimum (March 2004–March 2009) conditions in the
Northern Hemisphere. In the cusp region the SEA technique uses the time and
location of the mass density anomaly peaks as reference parameters. On
average, the amplitude of the relative density anomaly, ρrel,
does not depend on the solar cycle phase, local season, and IMF By sign.
Also, it is apparent that the amplitude of IMF By does not have a large
influence on ρrel, while the negative IMF Bz amplitude
prevailing about half an hour earlier is in good correlation with
ρrel. Both the zonal wind velocity and the large-scale FAC
(LSFAC) distribution exhibit a clear dependence on the IMF By sign.
Uzonal is directed towards dawn for both positive and negative IMF
By at all local seasons and for solar maximum and minimum conditions.
There is a systematic imbalance between downward (upward) and upward
(downward) large-scale FACs peaks equatorward and poleward of the reference
point, respectively, for the IMF By+ (By−) case. Relative
density enhancements appear halfway between region 1 and region 0 currents in
closer proximity to the upward FAC region. FAC densities and mass density
anomaly amplitudes are not well correlated, but it is apparent that there is
a close spatial relationship between ρrel and LSFAC. At this
point we cannot offer any simple functional relation between these two
variables, because there seem to be additional quantities controlling this
relation. |
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