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| Titel |
Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase |
| VerfasserIn |
J. R. T. Jussila, A. T. Aikio, S. Shalimov, S. R. Marple |
| 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 ; 22, no. 5 ; Nr. 22, no. 5 (2004-04-08), S.1675-1686 |
| Datensatznummer |
250014867
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| Publikation (Nr.) |
 copernicus.org/angeo-22-1675-2004.pdf |
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| Zusammenfassung |
Cosmic radio noise absorption (CNA) events associated with equatorward
drifting arcs during a substorm growth phase are studied by using
simultaneous optical auroral, IRIS imaging riometer and EISCAT incoherent
scatter radar measurements. The CNA is generally attributed to energetic
particle precipitation in the D-region. However, it has been argued that
plasma irregularities or enhanced electron temperature (Te) in the
E-region could also produce CNA. Both of the latter mechanisms are related to
intense electric fields in the ionosphere. We present two events which occur
during a substorm growth phase in the evening MLT sector. In both of the
events, an auroral arc is drifting equatorward, together with a region of CNA
(auroral absorption bay) located on the equatorward side and outside of the
arc. Both of the events are associated with enhanced D-region electron
density on the equatorward side of the auroral arc, but in the second event,
a region of intense electric field and enhanced electron temperature in the
E-region is also located on the equatorward side of the arc. We show that
in the studied events neither plasma instabilities nor enhanced Te play a
significant role in producing the measured CNA, but the CNA in the vicinity of
the equatorward drifting arcs is produced by D-region energetic electron
precipitation.
Key words. Ionosphere (auroral ionosphere; particle precipitation;
electric fields and currents) |
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