STRUCTURE OF MASS-LOADING SHOCKS .2. COMPARISON OF THEORY AND OBSERVATION AT COMET HALLEY

The multifluid diffusive model of G. P. Zank et al. (1994), which desc ribes the interaction of the solar wind with a cometary plasma in the outer coma, has been used to model the structure of the Halley bow sho ck. The theoretical results are compared to in situ observations made by Giotto. We compare the solar wind and cometary ion number densities and pressures upstream and through the quasiperpendicular and quasi-p arallel shocks (observed on the inbound and outbound legs of the encou nter, respectively). In general, good agreement is found between theor y and observations in terms of shock structure, strength, and location , especially for the quasi-parallel shock. The comparison between the quasi-perpendicular shock observations and theory is complicated by th e apparently nonstationary behavior of the shock, a feature which has been remarked upon by other investigators. The cometary bow shock appe ars to be an excellent example of an energetic-particle-mediated shock where the energetic particles comprise less than 10% of the total num ber density.