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P. A. Delamere, F. Bagenal, L. Ray (University of Colorado)
Observations of Comet 19P/Borrelly during the Deep Space 1 (DS1) flyby on September 22, 2001 with the Plasma Experiment for Planetary Exploration (PEPE) have shown asymmetries in the plasma environment boundaries (i.e. 10% solar wind slowing, cometary ion pickup, bow shock, sheath of heated plasma, cometopause and the center of ion density). All of the observed features were offset to the north of the nucleus-Sun line. Preliminary explanations for these asymmetries suggest that the coma itself is responsible due to, perhaps, well-collimated dayside jets directed northward of the nucleus. An alternative explanation involves the kinetics of the heavy pickup ions by the solar wind. In an attempt to understand the asymmetric Borrelly plasma environment we have used a hybrid plasma simulation to isolate the role of ion pickup. Our hybrid code uses a fluid treatment for the solar wind protons and massless electrons and a kinetic treatment for the pickup ions. Using an isotropic neutral cloud distribution, we are able to isolate the effects of pickup ion motion. Preliminary results suggest that the pickup ions can contribute significantly to the asymmetry in the plasma environment.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.