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

• Main Authors: S. Arvelius, M. Yamauchi, H. Nilsson, R. Lundin, Y. Hobara, H. Rème, M. B. Bavassano-Cattaneo, G. Paschmann, A. Korth, L. M. Kistler, G. K. Parks
• Format: Article
• Language: English
• Published: Copernicus Publications 2005-07-01
• Series: Annales Geophysicae
• Online Access: https://www.ann-geophys.net/23/1909/2005/angeo-23-1909-2005.pdf
• ISSN: 0992-7689; 1432-0576

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 <i>R_E</i>) 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 <i>R_E</i> geocentric distance and above 85deg ILAT location; (2) at 6-8 <i>R_E</i> 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 <i>R_E</i> 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.<p> <b>Keywords.</b> Magnetospheric physics (Magnetospheric configuration and dynamics, Solar wind-magnetosphere interactions)