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Ann. Geophys., 23, 535-543, 2005
www.ann-geophys.net/23/535/2005/
© European Geosciences Union 2005
Unusual heavy ion injection events observed by Freja
M. Yamauchi1, L. Eliasson1, R. Lundin1, and O. Norberg2
1Swedish Institute of Space Physics, Box 812, S-98128 Kiruna, Sweden
2Swedish Space Corporation - Esrange, Box 802, SE-98128 Kiruna, Sweden
Abstract. Heavy ion injection events (registered in the C+/N+/O+ mass channel) into
the ionosphere at 1700km height are surveyed using the Swedish-German Freja
satellite data. Heavy ion injections from the inner magnetosphere are mostly
found in the nightside sector with a few exceptions that occur on the
dayside. We report on these exceptional cases, particularly two specific
events which seem to have a different generation/transport mechanism of
heavy ions from the majority of cases: 1) mono-energetic heavy ion
injection near local noon with oxygen first and protons later; and 2) a
multiple heavy ion dispersion event at 9 MLT. Both events are unique without
any similar events in terms of dispersion pattern during the more than 2
years of the entire Freja operation, and these events are found during the
main phase of major magnetic storms (peak Dst is -144nT and -105nT). The
first event is probably of dayside origin but the exact mechanism to make
both energy filter and mass filter is unknown. The second event can be
traced back to one localized energization of dense oxygen with strong
pitch-angle anisotropy within 1000km distance from the spacecraft.
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