34th Solar Physics Division Meeting, June 2003
Session 6 Solar Wind and Heliosphere
Poster, Monday, June 16, 2003, 3:30-5:00pm, Mezzanine

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[6.09] MHD Modeling of the Halo Electrons in the Fast Solar Wind

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

A one-dimensional magnetohydrodynamic solar wind model is constructed to describe the behavior of the halo electrons in the fast electron-proton solar wind, assuming that the electrons are composed of two populations: the core and halo. The halo component is separated from the core electrons by increasing the heat deposition. It is shown that the model including only Coulomb collisions yields a much faster halo drift than observed if the halo temperature is in agreement with measured values. This supports the previous argument that some anomalous frictional processes caused by micro-instabilities and (or) wave-particle interactions exist in the solar wind. We show that these anomalous frictional processes can be approximated by enhanced Coulomb collisions together with a heat deposition that has a very large damping length. We find that beyond a certain heliocentric distance, say 20 RS, the anomalous frictional forces acting on the halo population are more important than the electric field force and the Coulomb collisional forces, and become the dominant factor inhibiting the core-halo drift.

This work was supported by NASA grants NAG5-10996 and NAG5-9564. Y. Chen was also supported by a predoctoral fellowship offered by the Smithsonian Astrophysical Observatory.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.