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| Titel |
Magnetospheric reconnection driven by solar wind pressure fronts |
| VerfasserIn |
A. Boudouridis, E. Zesta, L. R. Lyons, P. C. Anderson, D. Lummerzheim |
| 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 ; 22, no. 4 ; Nr. 22, no. 4 (2004-04-02), S.1367-1378 |
| Datensatznummer |
250014844
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| Publikation (Nr.) |
 copernicus.org/angeo-22-1367-2004.pdf |
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| Zusammenfassung |
Recent work has shown that solar wind dynamic pressure changes
can have a dramatic effect on the particle precipitation in the
high-latitude ionosphere. It has also been noted that the preexisting
interplanetary magnetic field (IMF) orientation can significantly
affect the resulting changes in the size, location, and intensity
of the auroral oval. Here we focus on the effect of pressure pulses
on the size of the auroral oval. We use particle precipitation data
from up to four Defense Meteorological Satellite Program (DMSP)
spacecraft and simultaneous POLAR Ultra-Violet Imager (UVI) images
to examine three events of solar wind pressure fronts impacting the
magnetosphere under two IMF orientations, IMF strongly southward
and IMF Bz nearly zero before the pressure jump. We show that
the amount of change in the oval and polar cap sizes and the local
time extent of the change depends strongly on IMF conditions prior
to the pressure enhancement. Under steady southward IMF, a remarkable
poleward widening of the oval at all magnetic local times and
shrinking of the polar cap are observed after the increase in solar
wind pressure. When the IMF Bz is nearly zero before the pressure
pulse, a poleward widening of the oval is observed mostly on the
nightside while the dayside remains unchanged. We interpret these
differences in terms of enhanced magnetospheric reconnection and
convection induced by the pressure change. When the IMF is southward
for a long time before the pressure jump, open magnetic flux is
accumulated in the tail and strong convection exists in the
magnetosphere. The compression results in a great enhancement of
reconnection across the tail which, coupled with an increase of
magnetospheric convection, leads to a dramatic poleward expansion
of the oval at all MLTs (dayside and nightside). For near-zero IMF
Bz before the pulse the open flux in the tail, available for
closing through reconnection, is smaller. This, in combination
with the weaker magnetospheric convection, leads to a more limited
poleward expansion of the oval, mostly on the nightside.
Key words. Magnetospheric physics (solar windmagnetosphere
interactions; magnetospheric configuration
and dynamics; auroral phenomena) |
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