Rapid Landau Heating of Martian Topside Ionospheric Electrons by Large-Amplitude Magnetosonic Waves

Atmospheric escape is a fundamental process in the long-term habitability evolution of terrestrial planets. Recent observations on Mars have found the concurrence of the severe ionospheric erosion and the large-amplitude, quasi-perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. Here we propose a new candidate mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. In contrast to the cyclotron resonance with oxygen atomic and molecular ions above the escape energies, the magnetosonic waves Landau-resonate with the thermal electrons at energy channels of the order of 0.01-0.1 eV. Through the Landau resonance over tens of minutes, the large-amplitude (12 nT) magnetosonic waves can heat the topside ionospheric electrons to similar to 2 times the normal temperature. The topside ionospheric electron heating could result in the enhancement of the ambipolar electric potential and eventually facilitate the escape of ionospheric plasma.