Articles | Volume 23, issue 5
28 Jul 2005
 | 28 Jul 2005

Statistics of high-altitude and high-latitude O+ ion outflows observed by Cluster/CIS

S. Arvelius, M. Yamauchi, H. Nilsson, R. Lundin, Y. Hobara, H. Rème, M.B. Bavassano-Cattaneo, G. Paschmann, A. Korth, L. M. Kistler, and G. K. Parks

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)