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Ann. Geophys., 25, 1359-1364, 2007
www.ann-geophys.net/25/1359/2007/
© European Geosciences Union 2007
Electron flux enhancement in the inner radiation belt during moderate magnetic storms
H. Tadokoro1, F. Tsuchiya1, Y. Miyoshi2, H. Misawa1, A. Morioka1, and D. S. Evans3
1Planetary Plasma and Atmospheric Research Center, Tohoku University, Aoba-ku, Sendai, 980-8578, Japan
2Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya, 464-8601, Japan
3Space Environment Center, NOAA, Boulder, CO 80305, USA
Abstract. During moderate magnetic storms, an electron channel (300–1100 keV) of the
NOAA satellite has shown sudden electron flux enhancements in the inner
radiation belt. After examinating the possibility of contamination by
different energetic particles, we conclude that these electron flux
enhancements are reliable enough to be considered as natural phenomena, at
least for the cases of small to moderate magnetic storms. Here, we define
small and moderate storms to be those in which the minimum Dst ranges
between −30 and −100 nT. The electron flux enhancements appear with over one
order of magnitude at L~2 during these storms. The enhancement is not
accompanied by any transport of electron flux from the outer belt.
Statistical analysis shows that these phenomena have a duration of
approximately 1 day during the period, starting with the main phase to the
early recovery phase of the storms. The flux enhancement shows a dawn-dusk
asymmetry; the amount of increased flux is larger in the dusk side. We
suggest that this phenomenon could not be caused by the radial diffusion but
would be due to pitch-angle scattering at the magnetic equator. The inner
belt is not in a stationary state, as was previously believed, but is
variable in response to the magnetic activity.
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