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Comets and their interactions with the solar wind are studied by means of large scale magnetohydrodynamic calculations with the aim to explain the observed structure and dynamics of the plasma tails.

Kometen und ihre Wechselwirkung mit dem Sonnenwind werden mit Hilfe von umfassenden magnetohydrodynamischen Modellrechnungen untersucht mit dem Ziel die beobachtete Struktur und Dynamik der Plasmaschweife zu erklaeren.

The hairy problems of these hairy stars are treated by the following group of more or less hairy people:

Hermann-Ulrich Schmidt
Rudolf Wegmann

Gone with the solar wind: Tail disconnection

Sometimes it happens that a large part of a cometary tail separates and moves away. A movie made by ESO shows such an event which occured at Comet Halley on April 8 1986. A tail disconnection indicates that something very dramatic in the solar wind and on the Sun must have happened. We have made MHD model calculations of the effect of an inclined interplanetary shock of Mach 2 on a comet with gas production 1e29 s-1. The movie shows the tail seen from the side. The frame covers 6e5 * 1e6 km. The 55 images cover a real time of 4.5 hours. We assume in the model that three hours after the shock an inverse shock restores the original solar wind conditions. A new tail forms and closes up to the receding old tail. Solar wind high speed streams and density enhancements in the solar wind can also cause tail disconnections as the movies show.

Comments to: Rudolph Wegmann ruw@mpa-garching.mpg.de