Title: Isotopic fractionation in slow and coronal hole associated solar wind

Authors: Kucharek, H, F.M. Ipavich, R. Kallenbach, B. Klecker, H. Grünwaldt, M. R. Aellig, P. Bochsler

Reference: IAU General Assembly, Manchester, August 2000

Solar matter is a geochemical reference for the original composition of the protosolar nebula from which the solar system formed. Therefore, the Sun represents the least biased sample of interstellar matter and the solar wind provides the most comprehensive source of information about solar isotopic abundance. From in situ measurements of the solar wind one obtains informations on the present-day isotopic composition of the outer convective zone of the Sun. The flow dynamic of the solar wind is determined by the magnetic topology of the flux tubes and is different for slow and fast solar wind, respectively. The slow solar wind originates from closed field line regions whereas the high speed solar wind is emitted from open flux tubes in coronal holes. Data from the Mass Time-of-Flight spectrometers MTOF and CTOF on board SOHO have been accumulated for time periods in which coronal hole and non-coronal hole type plasma has been detected by using different methods in order to determine the abundance ratios of magnesium isotopes in these two different source regions of the solar wind. The results as well as limits will be discussed in the context of existing theories.

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Last Update: April 11, 2001, Karine Issautier