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| Titel |
An auroral westward flow channel (AWFC) and its relationship to field-aligned current, ring current, and plasmapause location determined using multiple spacecraft observations |
| VerfasserIn |
M. L. Parkinson, J. A. Wild, C. L. Waters, Mark Lester, E. A. Lucek, P. M. E. Décréau |
| 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 ; 25, no. 1 ; Nr. 25, no. 1 (2007-02-01), S.59-76 |
| Datensatznummer |
250015763
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| Publikation (Nr.) |
 copernicus.org/angeo-25-59-2007.pdf |
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| Zusammenfassung |
| An auroral westward flow channel (AWFC) is a
latitudinally narrow channel of unstable F-region plasma with intense
westward drift in the dusk-to-midnight sector ionosphere. AWFCs tend to
overlap the equatorward edge of the auroral oval, and their life cycle is
often synchronised to that of substorms: they commence close to substorm
expansion phase onset, intensify during the expansion phase, and then decay
during the recovery phase. Here we define for the first time the
relationship between an AWFC, large-scale field-aligned current (FAC), the
ring current, and plasmapause location. The Tasman International Geospace
Environment Radar (TIGER), a Southern Hemisphere HF SuperDARN radar,
observed a jet-like AWFC during ~08:35 to 13:28 UT on 7 April 2001.
The initiation of the AWFC was preceded by a band of equatorward expanding
ionospheric scatter (BEES) which conveyed an intense poleward electric field
through the inner plasma sheet. Unlike previous AWFCs, this event was not
associated with a distinct substorm surge; rather it occurred during an
interval of persistent, moderate magnetic activity characterised by AL~−200 nT.
The four Cluster spacecraft had perigees within the dusk sector
plasmasphere, and their trajectories were magnetically conjugate to the
radar observations. The Waves of High frequency and Sounder for Probing
Electron density by Relaxation (WHISPER) instruments on board Cluster were
used to identify the plasmapause location. The Imager for
Magnetopause-to-Aurora Global Exploration (IMAGE) EUV experiment also
provided global-scale observations of the plasmapause. The Cluster fluxgate
magnetometers (FGM) provided successive measurements specifying the relative
location of the ring current and filamentary plasma sheet current. An
analysis of Iridium spacecraft magnetometer measurements provided estimates
of large-scale ionospheric FAC in relation to the AWFC evolution. Peak flows
in the AWFC were located close to the peak of a Region 2 downward FAC,
located just poleward of the plasmapause. DMSP satellite observations
confirmed the AWFC was located equatorward of the nightside plasmasheet,
sometimes associated with ~10 keV ion precipitation. |
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