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Ann. Geophys., 23, 1909-1916, 2005
www.ann-geophys.net/23/1909/2005/
© European Geosciences Union 2005
Statistics of high-altitude and high-latitude O+ ion outflows observed by Cluster/CIS
S. Arvelius1, M. Yamauchi1, H. Nilsson1, R. Lundin1, Y. Hobara1, H. Rème2, M.B. Bavassano-Cattaneo3, G. Paschmann4, A. Korth5, L. M. Kistler6, and G. K. Parks7
1Swedish Institute of Space Physics (IRF), Box 812, 98128 Kiruna, Sweden
2Centre d’Etude Spatiale des Rayonnements, Toulouse, France
3Instituto di Fisica dello Spazio Interplanetario, Roma, Italy
4Max-Planck-Institut für Extraterrestrische Physik, Garching, Germany
5Max-Planck-Institut für Sonnensystemforschung, Katlenburg-Lindau, Germany
6University of New Hampshire, Durham, USA
7Space Science Laboratory, UC Berkeley, USA
Abstract. The persistent outflows of O+ ions observed by
the Cluster CIS/CODIF instrument were studied statistically
in the high-altitude (from 3 up to 11 RE)
and high-latitude (from 70 to ~90 deg invariant latitude,
ILAT) polar region. The principal results are: (1) Outflowing
O+ ions with more than 1keV are observed above 10 RE geocentric distance and above 85deg ILAT location;
(2) at 6-8 RE geocentric distance, the latitudinal
distribution of O+ ion outflow is consistent with velocity
filter dispersion from a source equatorward and below the
spacecraft (e.g. the cusp/cleft); (3) however, at 8-12 RE
geocentric distance the distribution of O+ outflows cannot
be explained by velocity filter only. The results suggest
that additional energization or acceleration processes for
outflowing O+ ions occur at high altitudes and high
latitudes in the dayside polar region.
Keywords. Magnetospheric physics (Magnetospheric configuration
and dynamics, Solar wind-magnetosphere interactions)
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