X-ray tomography of a cometary bow shock

Abstract

The volume intensity of the cometary X-ray emission is enhanced behind the bow shock by a factor of up to three. This effect offers the opportunity to identify the bow shock by a tomographic method in X-ray images of comets. By an analysis of the X-ray data obtained by XMM-Newton from Comet C/2000 WM1 (LINEAR) we obtain information on the position, the shape and the structure of the bow shock of this comet. In particular, we get for the first time a global image of the subsolar part of the bow shock, which up to now has not been visited by spacecrafts. The shock is not a sharp discontinuous jump but rather a gradual transition in a region of about 40 000 km width. An asymmetry can well be explained by the inclination of the interplanetary magnetic field. Our results are consistent with theoretical expectations as well as with results from spacecraft observations.