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Article Dans Une Revue Annales Geophysicae Année : 2004

Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase

Résumé

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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Dates et versions

hal-00317349 , version 1 (18-06-2008)

Identifiants

  • HAL Id : hal-00317349 , version 1

Citer

J. R. T. Jussila, A. T. Aikio, S. Shalimov, S. R. Marple. Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase. Annales Geophysicae, 2004, 22 (5), pp.1675-1686. ⟨hal-00317349⟩

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