Simulating Impacts of Electron Precipitation on Mars' Nightside Ionosphere With an Empirical Model

With the aim of improving global simulations of the Martian ionosphere, we present an empirical model of 137 electron impact processes—including ionization, dissociation, and excitation—on the nightside of Mars, based on MAVEN in situ data collected between 2014 and 2019. The empirical model demonstrates the significant impact magnetic field conditions have on nightside ionization rates, with different magnetic topologies reversing trends previously seen in ionization dependence on magnetic field strength: closed field lines on the nightside show a decrease in ionization with stronger fields, while topologies where field lines connect to a source of plasma at one or both ends show an increase of ionization with stronger fields. This empirical model is coupled with magnetic fields from MHD simulations of the Martian magnetosphere, as input to the PCM-Mars and M-GITM thermosphere-ionosphere models, to provide a source of ionization on the nightside. Finally, we present new simulations of the global ionosphere with ionization sources on both the dayside and, for the first time, the nightside.