MAVEN Observations of the Kelvin-Helmholtz Instability Developing at the Ionopause of Mars

Abstract

Using the Mars Atmosphere and Volatile EvolutioN measurements, we observed a wave train of vortices in different developing phases of the Kelvin-Helmholtz (K-H) instability at the ionopause above the Martian northern hemisphere during 09:35:00–09:55:00 Universal Time on 24 March 2017. Based on the sawtooth-like oscillations in the magnetic fields associated with the quasi-periodic fluctuations in the ion densities, velocities, and total pressure, we identified three fully and two partially developed vortices. The wavelength of the K-H waves is ∼2 Martian radii and the period is ∼2 min. The magnetic topologies associated with the vortices are observed to change from draped in the magnetosheath to open in the transition region and finally to closed approaching the ionosphere. Significant ion loss caused by the K-H instability is observed. The total oxygen loss rate is estimated to be ∼1025 s−1, which is comparable to the global ion loss as previously estimated.