Limits on the Fractionation of Isotopes in the Solar Wind as Observed with SOHO/CELIAS/MTOF

R. Kallenbach, P. Bochsler, F.M. Ipavich, A.B. Galvin, R. Bodmer, S. Hefti, H. Kucharek, F. Gliem, H. Grünwaldt, M. Hilchenbach, B. Klecker, D. Hovestadt, and the CELIAS Team

Paper presented at the 31st ESLAB Symposium, 22-25 September 1997, ESTEC, Noordwijk, The Netherlands.

Information on the solar isotopic composition can be inferred from the study of solar wind abundances. Refractory elements show little variations in isotopic composition within different solar system materials. They can be used as isotopic reference to study fractionation processes in different solar wind regimes. We use the high-resolution mass spectrometer MTOF (MASS Time-of-Flight) of CELIAS onboard SOHO to determine the solar wind isotopic composition of magnesium and calcium from more than one year of data.

The isotopic composition of solar volatile elements such as helium and neon can only be derived from solar wind measurements. Our determination of the 20Ne/22Ne ratio with MTOF is in excellent agreement with the Apollo Foil measurements.

The results are discussed in the context of theoretical models that predict the efficiency of isotope fractionation in the slow and fast solar wind.

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Last Update: June 4, 1997, Peter Wurz