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| Titel |
Observations of an auroral streamer in a double oval configuration |
| VerfasserIn |
O. Amm, R. Nakamura, T. Takada, K. Kauristie, H. U. Frey, C. J. Owen, A. Aikio, R. Kuula |
| 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 ; 29, no. 4 ; Nr. 29, no. 4 (2011-04-27), S.701-716 |
| Datensatznummer |
250017006
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| Publikation (Nr.) |
 copernicus.org/angeo-29-701-2011.pdf |
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| Zusammenfassung |
| During the late evening and night of 14 September 2004, the nightside
auroral oval shows a distinct double oval configuration for several hours
after a substorm onset at ~18:45 UT. This structure is observed both
by the IMAGE satellite optical instruments focusing on the Southern
Hemisphere, and by the MIRACLE ground-based instrument network in
Scandinavia. At ~21:17 UT during the recovery phase of the substorm,
an auroral streamer is detected by these instruments and the EISCAT radar,
while simultaneously the Cluster satellites observe a bursty bulk flow in
the conjugate portion of the plasma sheet in the magnetotail. Our combined
data analysis reveals significant differences between the ionospheric
equivalent current signature of this streamer within a double oval
configuration, as compared to previously studied streamer events without
such a configuration. We attribute these differences to the presence of an
additional poleward polarization electric field between the poleward and the
equatorward portions of the double oval, and show with a simple model that
such an assumption can conceptually explain the observations. Further, we
estimate the total current transferred in meridional direction by this
recovery phase streamer to ~80 kA, significantly less than for
previously analysed expansion phase streamer events. Both results indicate
that the development of auroral streamers is dependent on the ambient
background conditions in the magnetosphere-ionosphere system. The auroral
streamer event studied was simultaneously observed in the conjugate Northern
and Southern Hemisphere ionosphere. |
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