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Three-dimensional multiscale MHD model of cometary plasma environments

Gombosi, Tamas I.; De Zeeuw, Darren L.; Häberli, Roman M. +1 more

First results of a three-dimensional multiscale MHD model of the interaction of an expanding cometary atmosphere with the magnetized solar wind are presented. The model starts with a supersonic and super-Alfvènic solar wind far upstream of the comet (25 Gm upstream of the nucleus) with arbitrary interplanetary magnetic field orientation. The solar…

Heating of the thermal electrons in the coma of comet P/Halley

Geiss, Johannes; Altwegg, Kathrin; Balsiger, Hans +1 more

In the inner coma of a comet the total ion (or electron) density results from an equilibrium between ion production and ion destruction. The ions are mainly produced by photoionization of cometary gas, whereas the main destruction process is dissociative recombination of molecular ions with electrons. The reaction rate for the recombination depend…

Cometary ion pressure anisotropies at comets Halley and Grigg-Skjellerup

Coates, A. J.; Neubauer, F. M.; Johnstone, A. D.

Cometary water group ions are the dominant population controlling the interaction of comets with the solar wind. The distribution function of this population has important effects on the overall structure and boundaries in the comet-solar wind interaction and on the plasma wave activity produced. In this paper we present new results on the behavio…

Upstream and downstream propagating waves generated by pickup ions near comet Halley

Glassmeier, K. -H.; Neubauer, F. M.; Krauklis, I. +3 more

It is well known that most of the Alfvén waves generated in the solar wind by cometary ion pickup are propagating upstream in the solar wind reference frame. However, the magnitude of the small proportion propagating downstream is extremely important because it controls the amount of ion acceleration driven by the second order Fermi process. The v…

Magnetic field structure in the comet Grigg-Skjellerup pileup region

Coates, A. J.; Neubauer, F. M.; Israelevich, P. L. +1 more

The position of the Giotto spacecraft relative to comet Grigg-Skjellerup is found from the draping geometry based on the vector magnetic field data. It is shown that Giotto passed the cometary nucleus on the nightside. The behavior of the magnetic field vectors exhibits two different types in the pileup region. In the outer pileup region, the magn…