Comet Grigg–Skjellerup Atmosphere Interaction With the Oncoming Solar Wind

Abstract

The interaction between the Comet P/Grigg-Skjellerup ionosphere and the oncoming solar wind is numerically simulated on the basis of the well-known gasdynamic single-fluid Biermann model. Numerical solutions are obtained using a discontinuity-fitting technique based on the implicit second-order Babenko-Rusanov method. The salient features of the interaction pattern for GS comet are nearly the same as in the previously considered case of the Comet P/Halley, although the gas productions of the two comets near the perihelion differ by an order of magnitude. The results of the numerical simulation are correlated with the data of onboard measurements performed during the `Giotto' encounter with GS comet in July 1992. The interaction region geometry, as well as the profiles of the plasma velocity and the disturbed magnetic field strength along the `Giotto' path, are compared. Theoretical and measured data are in a fairly good agreement, except for a near-nucleus region, where the MHD effects may become predominant. In general, the MHD effects appear to be more pronounced in the GS case, as compared with that of Halley comet, since during the `Giotto' – GS encounter the comet found itself in the `magnetic cloud' conditions.