Propagation of Transient Perturbations into a Planet's Exosphere: Molecular Kinetic Simulations

Abstract

The upper atmospheres of Mars and Titan, as well as those on many other planetary bodies, exhibit significant density variations vs. altitude that are interpreted as gravity waves. Such data is then used to extract vertical temperature profiles, even when such perturbations propagate through the transition region from a collision dominated regime and into a planet's exosphere. Since the temperature profile is critical for describing the upper atmospheric heating and evolution, we use molecular kinetic simulations to describe transient perturbations in a Mars-like upper atmosphere. We show that the standard methods for extracting the temperature profile can fail dramatically so that molecular kinetic simulations, calibrated to observed density profiles, are needed in this region of a planet's atmosphere.