A 3-dimensional Kinetic Particle Simulation of the Martian Hot Coronae and Upper Atmosphere: Mechanism, Structure, Variability, and Atmospheric Loss.

Abstract

The evaluation of the global atmospheric structure, variation, and loss rate is key to a better understanding of the physics that drives the current state of the Martian atmosphere. The production of energetic particles in the Martian upper thermosphere and exosphere results in the formation of the hot coronae, where most of the escape of neutral atoms occurs. The characterization of this hot population becomes challenging and complicated, since Mars has a strongly coupled atmospheric system from the lower to upper atmospheres, which requires a description of the transition from the collision-dominated regime to the collisionless regime. This thesis presents results of the 3D study of the Martian hot atomic coronae by introducing the significantly improved kinetic particle model, AMPS, and by coupling with the thermosphere/ionosphere model for various Martian conditions. The first comprehensive investigations of the 3D hot carbon corona are carried out by using the coupled framework linking the Mars-AMPS and MTGCM codes for different solar cycle and seasonal cases. The first coupling of the Mars-AMPS and M-GITM codes was completed for the hot oxygen corona study. The important source mechanisms described in simulations are analyzed by studying their dependencies on the local atmospheric variations. Utilizing the solar flux and orbital parameters, the solar cycle and seasonal variations are found to influence the hot coronae in different ways, requiring both two- or three-dimensional aspects of the macroscopic parameters from a local to global perspective. In this study of the hot carbon corona, the effects of the background atmosphere on the resulting hot carbon distribution have been examined by characterizing the local atmospheric structure and conditions. The spatial distributions of the parent molecule and ion of hot carbon are provided in comparison with the major thermospheric and ionospheric species. The oxygen distribution and the escape probability have been simulated for a wide range of the model parameters. The computed OI 1304Å brightness from our hot O corona shows both reasonable agreement and some discrepancies in comparisons with available observations. The current lack of data will be greatly alleviated by the in situ and remote measurements from the MAVEN mission.