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[57.13] A theoretical model for O⁺⁵ (O⁺⁷) ions in the fast solar wind

Y. Chen, R. Esser (Harvard-Smithsonian Center for Astrophysics), Y. Hu (University of Science and Technology of China)

We present a theoretical model for O⁺⁵ (O⁺⁷) ions as test particles in the fast solar wind, using a previous turbulence-driven four-fluid model to establish the background solar wind which consists of electrons, protons, alpha particles and O⁺⁶ ions. The O⁺⁵ (O⁺⁷) ions in our model and the O⁺⁶ ions in the background are driven by the same mechanism, say, the resonant cyclotron interaction or artificial heating additions. The ionization and recombination processes of O ions are taken into account. It is shown that the differential flow speeds between O⁺⁶ and O⁺⁵ or O⁺⁷, which are found to be in the range of 0.3 to 2, play very different roles in the formation of O charge states. This is due to discrepancy between the freezing-in distances of the two ion species. O⁺⁷ forms predominantly below 1.2 R_S too close to the Sun to develop a differential streaming between O ions. O⁺⁵ on the other hand, freezes-in at about 1.8 R_S where differential flows are well developed and therefore important for the formation of O⁺⁵ ions.

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Bulletin of the American Astronomical Society, 34
© 2002. The American Astronomical Soceity.