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

S. Arvelius (1) , M. Yamauchi (1) , Hans Nilsson (1) , R. Lundin (1) , Y. Hobara (1) , H. Rème (2) , M.B. Bavassano-Cattaneo (3) , G. Paschmann (4) , A. Korth (5) , L. M. Kistler (6) , G. K. Parks (7)

1 IRF - Swedish Institute of Space Physics [Kiruna]
2 CESR - Centre d'étude spatiale des rayonnements
3 Instituto di Fisica dello Spazio Interplanetario
4 MPE - Max-Planck-Institut für Extraterrestrische Physik
5 MPS - Max-Planck-Institut für Sonnensystemforschung = Max Planck Institute for Solar System Research
6 UNH - University of New Hampshire
7 SSL - Space Sciences Laboratory [Berkeley]

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 R_E) 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 R_E geocentric distance and above 85deg ILAT location; (2) at 6-8 R_E 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 R_E 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)

Domaines: Océan, Atmosphère; Sciences de la Terre

S. Arvelius, M. Yamauchi, Hans Nilsson, R. Lundin, Y. Hobara, et al.. Statistics of high-altitude and high-latitude O⁺ ion outflows observed by Cluster/CIS. Annales Geophysicae, 2005, 23 (5), pp.1909-1916. ⟨hal-00329420⟩