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Astron. Astrophys. 335, 691-702 (1998)

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Element fractionation in the solar chromosphere driven by ionization-diffusion processes

Hardi Peter

Max-Planck-Institut für Aeronomie, D-37191 Katlenburg-Lindau, Germany (hPeter@linmpi.mpg.de)

Received 11 August 1997 / Accepted 24 March 1998


An ionization-diffusion mechanism is proposed to understand the first ionization potential (FIP) fractionation as observed in the solar corona and the solar wind. The enrichment of the low-FIP elements ([FORMULA]10 eV) compared to the high-FIP elements in a large variety of phenomena, as e.g. slow and fast wind or polar plumes, is explained. Also the special behaviour of the heavy noble gases becomes perceptive and the absolute fractionation, i.e. in relation to hydrogen, can be calculated and fits well to the measurements. Additionally the theoretical velocity-dependence of the fractionation will be used to determine the velocities of the solar wind in the chromosphere. The main achievement of this paper is the explanation of a great variety of fractionation-related phenomena on the basis of one single model.

Key words: Sun: abundances – Sun: chromosphere – solar wind

Present address: High Altitude Observatory/NCAR, P.O. Box 3000, Boulder, CO 80307-3000, USA

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© European Southern Observatory (ESO) 1998

Online publication: June 18, 1998