Solar Wind Observations with SOHO/CELIAS

P. Bochsler, D. Hovestadt, H. Grünwaldt, M. Hilchenbach, F.M. Ipavich, K.-U. Reiche, W.I. Axford, H. Balsiger, A. Bürgi, M. Coplan, A.B. Galvin, J. Geiss, F. Gliem, G. Gloeckler, M. Hilchenbach, K.C. Hsieh, D.L. Judge, R. Kallenbach, B. Klecker, M.A. Lee, S. Livi, G.G. Managadze, E. Marsch, E. Möbius, M. Neugebauer, H.S. Ogawa, K.-U. Reiche, M. Scholer, M.I. Verigin, B. Wilken, and P. Wurz,

Paper presented at EPS Fall Meeting, Sevillia, Spain (1996).

CELIAS is an experiment which measures the mass, charge, and energy of solar wind and suprathermal particles. Three sensors, CTOF, MTOF, and STOF cover energies ranging from 0.1keV to several hundred MeV/nuc and masses ranging from hydrogen to nickel.

Charge states of minor elements in the solar wind are established in the inner corona as a result of their interaction with the hot abient electron gas. With increasing distance the electron decreases and ionization and recombination become sluggish such that charge states "freeze". It is thus possible to determine the temperature and density profiles of the inner corona by remote observation of charge state distributions of minor elements. CELIAS determines charge state distributions with an unprecedented time resolution due to the continous exposure to the solar wind onboard the three-axis stabilized spacecraft and due to its large geometrical factors.

The solar wind carries also information on the isotopic composition of the outer convection zone of the sun. The isotopic composition of many solar system objects including meteories, planetary atmospheres, and lunar samples has been determined for all elements with high accuracy. However, information on the solar isotopic composition has only been available for a few volatile elements. CELIAS now determines the isotopic composition for a wide range of elements thus providing relevant geochemical and astrophysical information.

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Last Update: October 8, 1996, Peter Wurz