Electron density variability in the day-side ionosphere of Mars: The role of gravity waves

Mars Atmosphere and Volatile EvolutioN (MAVEN) has observed oscillations in the density, velocity, and temperature of ionospheric plasma on Mars. Atmospheric gravity waves can be an underlying mechanism. We propose a linearized wave-electron interaction model adopting a Wentzel-Kramers-Brillouin approximation to explore the electron density variations in the Martian day-side ionosphere for two regions, which are dominated by crustal magnetic fields and horizontal draped interplanetary magnetic fields. Our model results reveal that the electron density fluctuations associated with the crustal magnetic fields and the draped magnetic fields range from similar to 40 per cent to similar to 83 per cent and similar to 29 per cent to similar to 125 per cent, respectively. The wave-induced vertical electron flux peaks occur in a region ranging from similar to 115 km to similar to 179 km altitude. These results are comparable to the satellite observations. We further investigate the effect of the Martian magnetic topology on the wave-induced electron fluxes and demonstrate that the electron motions associated with the propagating gravity waves can be significantly influenced by the magnetic field orientations. The wave-induced variations in the electron temperature, ion density, and magnetic field combined with a comprehensive gravity wave model will be studied in further work.

Automated summary

The MAVEN mission has observed oscillations in the densities, velocities, and temperatures of ionospheric plasma on Mars, which are likely caused by atmospheric gravity waves. A wave-electron interaction model has been proposed to investigate the electron density variations in different regions of the Martian ionosphere dominated by crustal magnetic fields and draped interplanetary magnetic fields. The model results show comparable patterns with satellite observations and reveal that electron density fluctuations range from 40% to 83% and 29% to 125% for the two regions, with wave-induced vertical electron flux peaks occurring at altitudes between 115 km and 179 km. The orientation of the Martian magnetic field has a significant influence on the electron motions associated with the propagating gravity waves.