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| Titel |
Behavior of substorm auroral arcs and Pi2 waves: implication for the kinetic ballooning instability |
| VerfasserIn |
T. F. Chang, C. Z. Cheng, C. Y. Chiang, A. B. Chen |
| 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 ; 30, no. 6 ; Nr. 30, no. 6 (2012-06-04), S.911-926 |
| Datensatznummer |
250017231
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| Publikation (Nr.) |
 copernicus.org/angeo-30-911-2012.pdf |
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| Zusammenfassung |
| We present synoptic observations of the 21 December 2006 substorm event by
the THEMIS ground-based All-Sky-Imagers, the ISUAL CCD Imager aboard the
FORMOSAT-2 satellite, the geosynchronous satellites and the ground-based
magnetometers, and discuss the implication of the observations. There are
three subsequent arc breakups with time separation of <1 min during
the substorm expansion phase. In particular, we investigated the mode number
of the substorm arc bead-like structure and the concurrent behavior of the
arc intensity, the westward electroject intensity, and the ground Pi2
pulsation amplitude. Prior to each arc breakup there was a clear
azimuthally-spaced bright spot structure along the arc with high mode number
(~140–180) and the arc intensity increased together with the westward
electrojet and the ground Pi2 pulsation amplitude under the arc. The Pi1
perturbations observed under the arc appeared at or after the arc breakup
started. This suggests that the Pi2 pulsation is related to the arc
formation. The Pi2 pulsation may be caused by the kinetic ballooning
instability (KBI) that is excited in the strong cross-tail current region.
The longitudinal extent of the earthward expansion front of the substorm
dipolarization region at the geosynchronous orbit is estimated from timings
of the energetic proton and electron injections and is roughly located
between ~19.50 MLT and ~23.00 MLT, which is consistent with the
corresponding longitudinal extent of the auroral substorm activity. |
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