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Ann. Geophys., 19, 643-648, 2001
www.ann-geophys.net/19/643/2001/
© European Geosciences Union 2001
Observation of low frequency electromagnetic activity at 1000 km altitude
N. Ivchenko and G. Marklund
Alfvén Laboratory, Royal Institute of Technology, Stockholm, Sweden
Abstract. We present a statistical
study of low frequency fluctuations of electric and magnetic fields, commonly
interpreted as Alfvénic activity. The data base consists of six months of
electric and magnetic field measurements by the Astrid-2 microsatellite. The
occurrence of the events is studied with respect to the location and general
activity. Large regions of broadband Alfvénic activity are persistently
observed in the cusp/cleft and, during the periods of high geo-magnetic
activity, also in the pre-midnight sector of the auroral oval.
Key words. Ionosphere (auroral
ionosphere) – Space plasma physics (waves and instabilities) –
Magnetospheric physics (magnetosphere-ionosphere interactions)
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