On the diamagnetic effect associated with the ion pile-up region in the coma of comet Halley

Abstract

The ion pile-up region in the comet Halley ionosphere observed on the inbound leg of the Giotto trajectory is accompanied by a decrease of the magnetic field strength. This magnetic field dip is explained by means of a diamagnetic effect of the plasma density increase in the pile-up region. Maximum of the plasma pressure seems to coincide with the maximum of the ion density. We arrived at the conclusion that the electron temperature profile should also possess a maximum in this region. This fact corroborates the results by Eberhardt and Krankowsky (1995). No magnetic effect of the enhanced plasma density was observed near the anticipated position of the ion pile-up region for the outbound leg of the trajectory. Thus, we conclude that the ion pile-up in the inner cometary coma (as it was observed on the inbound leg of the Giotto trajectory) is a transient (spatially and/or temporarily) phenomenon rather than a permanent feature.