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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 2
Ann. Geophys., 23, 535–543, 2005
https://doi.org/10.5194/angeo-23-535-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 535–543, 2005
https://doi.org/10.5194/angeo-23-535-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  28 Feb 2005

28 Feb 2005

Unusual heavy ion injection events observed by Freja

M. Yamauchi1, L. Eliasson1, R. Lundin1, and O. Norberg2 M. Yamauchi et al.
  • 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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