The Fe/O Elemental Abundance Ratio in the Solar Wind

Authors: M.R. Aellig, P. Bochsler, P. Wurz, H. H Grünwaldt, S. Hefti, H. Holweger, F.M.Ipavich, and B. Klecker.

Submitted abstract to the Solar Wind 9 Conference in Nantucket, MA, USA, 5-9 October, 1998.

We derive the Fe/O elemental abundance ratio in the solar wind from SOHO/ CELIAS/CTOF data. Analyzed in different solar wind regimes this ratio is indicative of the strength of the FIP fractionation process because iron is a low FIP element and oxygen is a high FIP element. For coronal hole solar wind and the slow solar wind we obtain a good agreement with previously published values from other missions. In addition, we find, as a function of the solar wind drift speed, a smooth transition of the Fe/O ratio between these two regimes, i.e., between about 350 and 500 km/s. We discuss the implications of this speed dependence with respect to existing FIP effect models. The Fe/O abundance ratio is also correlated with the oxygen freeze-in temperature and a preliminary He/H abundance ratio derived from SOHO/CELIAS/MTOF data which both are indicators for the source region of the solar wind.

Furthermore, we assess the accuracy of the determination of the photospheric abundance ratios to discuss the absolute values of the fractionation factors.

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Last Update: September 8, 1998 by James Weygand