MAVEN Observations of the Kelvin‐Helmholtz Instability Developing at the Ionopause of Mars. Issue 7 (29th March 2022)

• Record Type: Journal Article
• Authors: Wang, Xing; Xu, Xiaojun; Ye, Yudong; Wang, Jing; Wang, Ming; Zhou, Zilu; Chang, Qing; Xu, Qi; Xu, Jiaying; Luo, Lei; He, Peishan; Cheng, Shaoguan
• Is Part Of: Geophysical research letters. Volume 49:Issue 7(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-03-29
• Subjects: Kelvin‐Helmholtz instability -- ion loss -- MAVEN; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL098673
• Languages: English
• ISSNs: 0094-8276

Abstract

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 ∼10 25 s −1, which is comparable to the global ion loss as previously estimated. Plain Language Summary: Shear‐driven Kelvin‐Helmholtz (K‐H) instability can form along the boundary of the solar wind interaction with non‐magnetic planets (such as Venus and Mars). Previous studies reported partially and fully developed K‐H vortices at the Martian induced magnetosheath. In this study, we directly observed both types of the K‐H vortices during the developing process of the K‐H instability at the Martian ionopause. The magnetic topologies associated with the K‐H vortices change from draped in the magnetosheath to open in the transition region and to closed approaching the ionosphere. The K‐H instability can be an effective mechanism that leads to ion escape at Mars. A large number of ions within the K‐H vortices are observed to escape from Mars. The loss rate of oxygen caused by the K‐H instability is estimated to be significantly high. Our results confirm that the K‐H instability is important for the Martian ion loss. Key Points: We report a wave train of Kelvin‐Helmholtz (K‐H) vortices during different developing phases of the K‐H instability at the ionopause of Mars The wavelength of the K‐H waves is ∼2 Martian radii and the period is ∼2 min; the magnetic topologies within the K‐H vortices changed The estimated loss rate of oxygen caused by the K‐H instability is on the order of 10 25 s −1