DSMC Simulation of the Cometary Coma

The study of the comet coma, or its tenuous atmosphere, is a major space application of rarefied gas dynamics, which requires modeling the gas flow in a wide range of Knudsen number. For weak to moderate comets, only the subsolar region of the coma is in a collision dominated regime. In the low density regions of the upper atmospheres of the planets and the planetary satellites and the middle to outer coma of comets the intermolecular mean free path becomes longer then the characteristic length of the problem, which makes using of conventional methods of computational gas dynamics problematic and implies the requirement to model the system based on the Boltzmann equation. Here we present results of a first application of a fully parallelized implementation of Direct Simulation Monte Carlo for axisymmetric cometary comae