THE FLOW IN THE COMETOSHEATH OF COMET HALLEY

A quasi-one-dimensional, single-fluid model is used to examine the com etosheath flow along the Sun-comet axis at comet, Halley. The effects of mass loading, dissociative recombination, magnetic field line curva ture, ion-neutral drag, and flow divergence on the submagnetosonic flo w in this region are discussed. In particular, the inclusion of the fl ow divergence, which is achieved by allowing the central flow tube are a to increase toward the comet, is necessary to bring the cometosheath flow to stagnation at the subsolar point of the ionopause. The cometo sheath flow and field profiles are determined for two assumed values o f the electron-ion dissociative recombination rate. The model calculat ions performed using the higher recombination rate are shown to be in better agreement with the Giotto data at comet Halley.