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| Titel |
The relationship of thermospheric density anomaly with electron temperature, small-scale FAC, and ion up-flow in the cusp region, as observed by CHAMP and DMSP satellites |
| 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 ; 31, no. 3 ; Nr. 31, no. 3 (2013-03-20), S.541-554 |
| Datensatznummer |
250019013
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| Publikation (Nr.) |
 copernicus.org/angeo-31-541-2013.pdf |
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| Zusammenfassung |
| We present in a statistical study a comparison of thermospheric mass density
enhancements (ρrel) with electron temperature (Te),
small-scale field-aligned currents (SSFACs), and vertical ion velocity
(Vz) at high latitudes around noon magnetic local time (MLT).
Satellite data from CHAMP (CHAllenging Minisatellite Payload) and DMSP (Defense Meteorological Satellite Program) sampling the Northern Hemisphere during
the years 2002–2005 are used. In a first step we investigate the
distribution of the measured quantities in a magnetic latitude (MLat) versus
MLT frame. All considered variables exhibit prominent peak amplitudes in the
cusp region. A superposed epoch analysis was performed to examine causal
relationship between the quantities. The occurrence of a thermospheric
relative mass density anomaly, ρrel >1.2, in the cusp region is
defining an event. The location of the density peak is taken as a reference
latitude (Δ MLat = 0°). Interestingly, all the considered
quantities, SSFACs, Te, and Vz are co-located with the density
anomaly. The amplitudes of the peaks exhibit different characters of
seasonal variation. The average relative density enhancement of the more
prominent density peaks considered in this study amounts to 1.33 during all
seasons. As expected, SSFACs are largest in summer with average amplitudes
equal to 2.56 μA m−2, decaying to 2.00 μA m−2 in winter. The event related
enhancements of Te and Vz are both largest in winter (Δ
Te =730 K, Vz =136 m s−1) and smallest in summer (Δ Te
= 377 K, Vz = 57 m s−1. Based on the similarity of the seasonal
behaviour we suggest a close relationship between these two quantities. A
correlation analysis supports a linear relation with a high coefficient
greater than or equal to 0.93, irrespective of season. Our preferred
explanation is that dayside reconnection fuels Joule heating of the
thermosphere causing air upwelling and at the same time heating of the
electron gas that pulls up ions along affected flux tubes. |
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