CELIAS/CTOF Measurement of O5+: A Key to the Maze of Coronal Electron Velocity Distribution

Authors: H. Gruenwaldt, M. Hilchenbach, E. Marsch, P. Bochsler, and F.M. Ipavich
Reference: Solar Wind 9, AIP conference proceedings 471, New York, Editors: S. R. Habbal, R. Esser, J. Hollweg, and P. Isenberg, 1999.

The classical link between the frozen-in solar wind ion charge distribution and the inferred coronal electron temperature has been ruled for long by the asumption of a Maxwellian velocity distribution of the electrons. After theoretical negotiation of this assumption (Owocki & Scudder 1983), recent experience from the observation of O VI lines by UV instruments on SOHO has raised serious doubts as to a considerably overestimated temperature, in contrast to the very low upper limits of O5+ as solar wind constituent seen by Ulysses in high speed wind. From CELIAS/CTOF data it has now been possible to measure abundance figures for solar wind conditions of slow to moderate speed from near streamer belt source regions, rising with growing speed to values almost an order of magnitude higher than the limits seen before. The coincident presence of high and low O charge states is understood by energetic tail electrons ionising, and cool core electrons being part of radiative recombination.

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Last Update: October 20, 1999, James Weygand