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| Titel |
Radar detection of a localized 1.4 Hz pulsation in auroral plasma, simultaneous with pulsating optical emissions, during a substorm |
| VerfasserIn |
R. Cosgrove, M. Nicolls, H. Dahlgren, S. Ranjan, E. Sánchez, R. Doe |
| 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 ; 28, no. 10 ; Nr. 28, no. 10 (2010-10-29), S.1961-1979 |
| Datensatznummer |
250016903
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| Publikation (Nr.) |
 copernicus.org/angeo-28-1961-2010.pdf |
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| Zusammenfassung |
| Many pulsating phenomena are associated with the auroral substorm.
It has been considered that some of these phenomena involve kilometer-scale
Alfvén waves coupling the magnetosphere and ionosphere. Electric field
oscillations at the altitude of the ionosphere are a signature of
such wave activity that could distinguish it from other sources of
auroral particle precipitation, which may be simply tracers of magnetospheric
activity. Therefore, a ground based diagnostic of kilometer-scale
oscillating electric fields would be a valuable tool in the study
of pulsations and the auroral substorm. In this study we attempt to
develop such a tool in the Poker Flat incoherent scatter radar (PFISR).
The central result is a statistically significant detection of a 1.4 Hz
electric field oscillation associated with a similar oscillating
optical emission, during the recovery phase of a substorm. The optical
emissions also contain a bright, lower frequency (0.2 Hz) pulsation
that does not show up in the radar backscatter. The fact that higher
frequency oscillations are detected by the radar, whereas the bright,
lower frequency optical pulsation is not detected by the radar, serves
to strengthen a theoretical argument that the radar is sensitive to
oscillating electric fields, but not to oscillating particle precipitation.
Although it is difficult to make conclusions as to the physical mechanism,
we do not find evidence for a plane-wave-like Alfvén wave; the detected
structure is evident in only two of five adjacent beams. We emphasize
that this is a new application for ISR, and that corroborating results
are needed. |
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