Cosmic radio noise absorption events associated with equatorward drifting arcs during a substorm growth phase
| Autor: | S. R. Marple, Anita Aikio, S. Shalimov, J. Jussila |
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| Přispěvatelé: | Department of Physical Sciences [Oulu], University of Oulu, Schmidt United Institute of Physics of the Earth [Moscow] (IPE), Russian Academy of Sciences [Moscow] (RAS), Department of Communication Systems, EGU, Publication |
| Jazyk: | angličtina |
| Rok vydání: | 2004 |
| Předmět: |
Atmospheric Science
Electron density Incoherent scatter Electron precipitation [SDU.STU]Sciences of the Universe [physics]/Earth Sciences Relativistic particle Physics::Geophysics Substorm Riometer Earth and Planetary Sciences (miscellaneous) lcsh:Science Physics [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere [SDU.OCEAN] Sciences of the Universe [physics]/Ocean Atmosphere lcsh:QC801-809 Geology Astronomy and Astrophysics Geophysics lcsh:QC1-999 lcsh:Geophysics. Cosmic physics Space and Planetary Science Physics::Space Physics [SDU.STU] Sciences of the Universe [physics]/Earth Sciences Electron temperature lcsh:Q Ionosphere lcsh:Physics |
| Zdroj: | Annales Geophysicae Annales Geophysicae, European Geosciences Union, 2004, 22 (5), pp.1675-1686 Scopus-Elsevier Annales Geophysicae, Vol 22, Pp 1675-1686 (2004) Annales Geophysicae, Vol 22, Iss 5, Pp 1675-1686 (2004) |
| ISSN: | 0992-7689 1432-0576 |
| Popis: | 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) |
| Databáze: | OpenAIRE |
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