The Iron, Silicon, and Oxygen Abundance in the Solar Wind Measured with SOHO/CELIAS/MTOF

Author: P. Wurz, M.R. Aellig, F.M. Ipavich, S. Hefti, P. Bochsler, and A.B. Galvin.

Submitted an abstract to the AGU fall meeting 1998.

From data collected with the MTOF sensor of the CELIAS instrument on board the SOHO spacecraft we derived the elemental abundance ratios for Si/O and Fe/O in the solar wind. Since Si and Fe are elements with a low first ionization potential (FIP) and oxygen is a high FIP element, these abundance ratios are valuable diagnostic tools for the study of the FIP fractionation process. The abundance ratios we find for slow and fast solar wind are commensurate with published values for interstream and coronal hole type solar wind. Between these two extreme cases of solar wind flow we find a continuous decrease of the abundance ratios for increasing solar wind speed, from a high value indicative of solar wind originating from the streamer belt to low values associated with flow from coronal holes. This continuous decrease of the abundance ratios can be understood in terms of a fractionation depending on the chromospheric mass flow speed, as has been put forward in a recent model.

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Last Update: Septembet 8, 1998, James Weygand