THE INTERACTION BETWEEN THE SOLAR-WIND AND THE COMET P HALLEY ATMOSPHERE - OBSERVATIONS VERSUS THEORETICAL PREDICTIONS

The results of a self-consistent gasdynamic model of the interaction b etween the solar wind and a comet ionosphere developed by the authors are compared with the data of onboard measurements performed during sp acecraft encounters with Comet Halley in March 1986. Theoretical profi les of plasma density and velocity, as well as magnetic field strength , are in good agreement with the experimental ones. The calculated pos ition of the bow shock wave in the solar wind coincides with the measu rements. The existence of a ''shear layer'', predicted by the theoreti cal model, is confirmed empirically. This layer where the plasma densi ty grows catastrophically was called a ''heavy ion mantle'' by experim enters. Singularities in the observed profiles in the vicinity of the comet nucleus are discussed from a theoretical point of view. A veloci ty and temperature jump which occurred on the inward leg of Giotto's p ath at a distance of 5 10(3) km from the nucleus is interpreted as the crossing of the inner shock wave in the ion outflow from the comet. P ossible ways to improve the gasdynamic model are discussed.