Hot carbon corona in Mars' upper thermosphere and exosphere: 2. Solar cycle and seasonal variability

Abstract

AbstractThis work presents the variability over seasons (i.e., orbital position) and solar cycle of the Martian upper atmosphere and hot carbon corona. We investigate the production and distribution of energetic carbon atoms and the impacts on the total global hot carbon loss from dominant photochemical processes at five different cases: AL (aphelion and low solar activity), EL (equinox and low solar activity), EH (equinox and high solar activity), PL (perihelion and low solar activity), and PH (perihelion and high solar activity). We compare our results with previously published results but only on the limited cases due to the dearth of studies on solar EUV flux and seasonal variabilities. Photodissociation of CO and dissociative recombination of CO+ are generally regarded as the two most important source reactions for the production of hot atomic carbon. Of these two, photodissociation of CO is found to be the dominant source in all cases considered. To describe self‐consistently the exosphere and the upper thermosphere, a 3‐D kinetic particle simulator, the Adaptive Mesh Particle Simulator, and the 3‐D Mars Thermosphere General Circulation Model are one‐way coupled. The basic description of this hot carbon calculation can be found in the companion paper to this one. The spatial distributions and profiles of density and temperature and atmospheric loss rates are discussed for the cases considered. Finally, our computed global escape rate of hot carbon ranges from 5.28 × 1023 s−1 (AL) to 55.1 × 1023 s−1 (PL).