HYBRID FLUID KINETIC APPROACH TO PLANETARY-ATMOSPHERES - AN EXAMPLE OF AN INTERMEDIATE-MASS BODY/

The atmosphere of an intermediate mass planetary body is calculated in a self-consistent fashion by the use of a hybrid fluid/kinetic theory approach on massively parallel computers. Assuming a spherical atmosp here and a heating layer, this technique is used to obtain the atmosph ere from the collisional hydrodynamic regime, through the quasi-collis ional nonlinear kinetic regime, and into the self-collisionless linear kinetic regime. The results display significant nonequilibrium phenom ena in both macroscopic variables such as temperature and microscopic variables such as the velocity distribution. Comparison with a standar d hydrodynamic model demonstrates substantial differences. This method which is valid for all Knudsen numbers can be easily generalized to m ore complex problems and should be a powerful tool to study the struct ure, dynamics, and evolution of planetary atmospheres.