Electrodynamical Interaction Between Comet Shoemaker-levy 9 And Jupiter's Magnetosphere

Abstract

The electrodynamical interaction between Jupiter and comet Shoemaker-Levy 9, which is expected to impact on Jupiter around July 20, 1994, has been investigated. The comet consists of a train of 21 or so nuclei surrounded by neutral gas clouds. Because of electron impact ionization and photo-ionization the neutral clouds will become partly ionized when they pass through the plasma in the magnetosphere. Both the comet`s motion towards Jupiter and the co-rotation of the Jovian magnetosphere inside 20 R{sub J} contribute to give the plasma in the clouds a velocity across B, and thus an induced electric field is produced in the comet`s rest frame. The authors discuss here the possibility that the electrodynamical interaction between Jupiter and the ionized comet clouds might drive processes which can be observed prior to the impact of Shoemaker-Levy 9 on Jupiter itself. Fortunately there is already a suitable object within the Jovian magnetosphere on which to base a model for such interaction: the Jupiter-Io system has been described as an archetype for the coupling between a large conductor and a magnetized plasma in relative motion. In the Jupiter-Io system, currents of several MA flow long distances along the magnetic field. Associated with these currentsmore » is the Jovian Decametric Radiation, one of the strongest radio sources in the solar system, and for which the excitation mechanisms is still not completely understood. The Shoemaker-Levy comet can theoretically supply ions to Jupiter`s magnetosphere at a rate not so far below Io`s, and will have a higher velocity relative to Jupiter, and could therefore conceivably drive similar processes. Based on a numerical model, the authors predict that any electromagnetic radiation caused by the interaction between comet Shoemaker-Levy 9 and the Jovian magnetosphere will be rather insignificant and very difficult to detect.« less