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Ann. Geophys., 26, 1335-1339, 2008
www.ann-geophys.net/26/1335/2008/
© European Geosciences Union 2008
Average profiles of the solar wind and outer radiation belt during the extreme flux enhancement of relativistic electrons at geosynchronous orbit
R. Kataoka1 and Y. Miyoshi2
1RIKEN (The Institute of Physics and Chemical Research) 2-1, Hirosawa, Wako, 351-0198, Japan
2Solar-Terrestrial Environment Laboratory, Nagoya University, Furo-cho, Nagoya, Aichi, 464-8601, Japan
Abstract. We report average profiles of the solar wind and outer radiation belt
during the extreme flux enhancement of relativistic electrons at
geosynchronous orbit (GEO). It is found that seven of top ten extreme events
at GEO during solar cycle 23 are associated with the magnetosphere inflation
during the storm recovery phase as caused by the large-scale solar wind
structure of very low dynamic pressure (<1.0 nPa) during rapid speed
decrease from very high (>650 km/s) to typical (400–500 km/s) in a few
days. For the seven events, the solar wind parameters, geomagnetic activity
indices, and relativistic electron flux and geomagnetic field at GEO are
superposed at the local noon period of GOES satellites to investigate the
physical cause. The average profiles support the "double inflation"
mechanism that the rarefaction of the solar wind and subsequent
magnetosphere inflation are one of the best conditions to produce the
extreme flux enhancement at GEO because of the excellent magnetic
confinement of relativistic electrons by reducing the drift loss of trapped
electrons at dayside magnetopause.
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