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| Titel |
Cross-tail current evolution during substorm dipolarization |
| VerfasserIn |
A. T. Y. Lui |
| 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. 6 ; Nr. 31, no. 6 (2013-06-27), S.1131-1142 |
| Datensatznummer |
250019057
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1131-2013.pdf |
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| Zusammenfassung |
| We examine evolution of the cross-tail current during
substorm current disruption/dipolarization using observations from two
satellites in the near-Earth magnetotail at the downtail distances of 8–9 RE.
By choosing times when these two satellites are separated, mainly in
the north–south distance in the tail current sheet, precise determination of
current density in the layer embedded between these satellites can be
obtained with Ampère's law. Two such events are examined and several common
features are found. The current densities in the layer embedded by the two
satellites were reduced by ~ 40–70% during substorm
dipolarization. The changes in current densities have the fast kinetic timescale, i.e., in seconds, implying a kinetic process for current
disruption/dipolarization. The estimated power within the current layer was
mainly dissipative in the dawn–dusk direction and mainly dynamo in the
Sun–tail direction that is needed to drive the north–south substorm current
system in the ionosphere. Remote sensing of the energization site with the
ion sounding technique shows that the energization site was initially
earthward of the satellite and moved down the tail at later times. Breakdown
of the frozen-in condition occurred intermittently during the disturbance
interval. These features provide important clues to the substorm onset
process. |
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