Monte Carlo study of the escape of a minor species

The problem of the escape of a minor species through a major species for different mass ratios is considered. The gravitational force is simulated by a barrier that reflects particles that reach the upper boundary with an up-going velocity greater than an escape velocity. Different collision models (Maxwell molecule and hard sphere) and different values of escape velocity are considered. A Monte Carlo simulation is used to compute the minor species distribution function, density, drift velocity, parallel and perpendicular temperatures, and parallel and perpendicular heat fluxes. The Monte Carlo solutions are shown to be consistent with the results of kinetic solutions. The present study is of interest in connection with such space-physics problems as the Jeans escape of light atoms from a planetary atmosphere and ion escape in the terrestrial polar wind.