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| Titel |
Seasonal variation of the ion upflow in the topside ionosphere during SAPS (subauroral polarization stream) periods |
| VerfasserIn |
H. Wang, 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. 9 ; Nr. 31, no. 9 (2013-09-06), S.1521-1534 |
| Datensatznummer |
250086103
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1521-2013.pdf |
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| Zusammenfassung |
| A statistical study has been performed by using two years of DMSP (Defense
Meteorological Satellite Program)
plasma observations to investigate the seasonal effect of SAPS
(subauroral polarization stream) on the ion upflow in the duskside
ionosphere of the Northern Hemisphere. There are obvious upflows
occurring in the topside ionosphere around the SAPS region,
exceeding 200 m s−1 at winter solstice, indicating an important
relationship between SAPS and the local plasma upward motion. Both
SAPS and ion upward velocities show similar seasonal variations,
largest in winter and smallest in summer, irrespective of
geomagnetic activity. A good correlation is found and a linear
relationship is derived between SAPS and the ion upflow
velocities. During December solstice the average upflow flux can reach
about 2 × 108 cm−2 s−1 for more disturbed periods,
which is comparable to the typical upflow flux in the dayside cusp
region. The depression of the ion temperatures around the peak
SAPS region can be understood in terms of the adiabatic cooling.
The hot ion cools down when expanding into the low ion
concentration region. The electron temperature elevates around the
SAPS region because of the reduced Coulomb cooling in the low ion
density region. Both the changes of ion and electron temperatures
are larger in winter than in summer, however, for Kp < 4 the
electron temperatures are almost seasonably independent. The present work
highlights the important role of the SAPS-related frictional
heating at mid-latitudes on the local formation of the strong
upward flow, which might provide a direct ionospheric ion source
for the ring current and plasmasphere in the duskside sector. |
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