Molecular kinetic simulations of transient perturbations in a planet's upper atmosphere

The upper atmospheres of planetary bodies can exhibit significant density perturbations as indicated by in situ spacecraft and remote sensing observations. As density vs. altitude data are often used to extract vertical temperature profiles, we examine their validity when such perturbations occur in the region where the atmosphere transitions from collision dominated and to nearly collisionless. Since an accurate temperature profile is critical for describing the chemistry and physics of the upper atmosphere, we use molecular kinetic simulations to examine the vertical propagation of transient perturbations. We find that in an atmosphere's transition region, the standard methods for extracting a 1D temperature profile can be unreliable and examine how the composition vs. altitude is transiently modified by simulating an atmosphere with Mars-like properties. These results suggest that molecular kinetic simulations, calibrated to observed density profiles, could be needed to fully understand the energy transfer and heating in this region of a planet's atmosphere.