A Comparison between 3D Model Results Using Two Different Collision Schemes: Forward Scattering vs. Hard Sphere Collision

The recent observations of the Martian geomorphology suggest that water has played a critical role in forming the present status of the Martian atmosphere and environment. The inventory of water has been depleted throughout the planet's geologic time via various mechanisms from the surface to the uppermost atmosphere where the Sun-Mars interaction occurs. During the current epoch, dissociative recombination of O2+ is suggested as the main nonthermal mechanism that regulates the escape of atomic O, forming the hot O corona. A nascent hot O atom produced deep in the thermosphere undergoes collisions with the background thermal species, where the particle can lose energy and become thermalized before it reaches the collisionless regime and escape. The major hot O collisions with the background species that contribute to the thermalization of hot O are Ohot-Ocold, Ohot-CO2,cold, Ohot-COcold, and Ohot-N2,cold. In order to describe these collisions, there have been different collisions schemes used by the previous models. One of the most realistic descriptions involves using angular differential cross sections, and the simplest approach is using isotropic collision cross sections. Here, we present a comparison between the 3D model results using two different collision schemes to find equivalent hard sphere collision cross sections that satisfy the effects from using forward scattering cross sections. We adapted the newly calculated angular differential cross sections to the major hot O collisions. The hot O corona is simulated by coupling our Mars application of the 3D Adaptive Mesh Particle Simulator (M-AMPS) [Tenishev et al., 2008, 2013] and the Mars Global Ionosphere-Thermosphere Model (M-GITM) [Bougher et al., 2015].