Magnetically Controlled Ionosphere of Mars: A Model Analysis with Neutral Wind Effects

We use our 1-D chemical diffusive model to quantify the physical processes necessary to interpret the day-side ionospheric measurements acquired with radio occultation techniques at the southern high-latitude region of Mars, where the crustal magnetic field is strong and near-vertical in orientation. To interpret the measured ionospheric structure at altitudes where plasma transport dominates, we find it is necessary to impose field-aligned vertical plasma drifts caused by the motion of neutral winds. The most interesting finding of
this study is that both upward (between 110 m/s and 150 m/s) and downward (between -55 m/s and -120 m/s) drifts are required to maintain the topside Ne distribution comparable with the measured distribution. We also find that a fixed velocity boundary condition at the upper boundary with a sizeable upward ion velocity is needed to encounter any unexpected ion accumulation in the topside ionosphere to limit the Martian ion outflow. Given the complex nature of neutral dynamics and its relationship to plasma transport processes over magnetic anomalies, we consider that a simple model, such as we have developed, is still capable of yielding valuable insights relating to the neutral wind system at Mars.