Magnetic Reconnection in the Martian Magnetotail: Occurrence Rate and Impact on Ion Loss

The current sheet is crucial in releasing magnetic free energy in cosmic plasmas via fast magnetic reconnection or wave excitation. This research investigates the characteristics of the Martian tail current sheet by analyzing data acquired from the Mars Atmosphere and Volatile EvolutioN spacecraft over 7 years. For the first time, we find that approximately 15% of the current sheet events display reconnection signatures, including Hall magnetic fields and fast proton flows. These reconnecting current sheets are detected more frequently on Mars than on Earth. The Martian tail current sheet is first demonstrated to be on the proton scale, which can explain the high reconnection occurrence rate. The research also reveals that the current sheets are thinner in regions closer to Mars and in the -E hemisphere. On average, reconnecting current sheets carry high fluxes of protons rather than oxygen ions. As a ubiquitous plasma configuration in various cosmic plasma environments, the current sheet is critical in facilitating the release of magnetic energy through explosive processes, such as fast magnetic reconnection. On Earth, magnetic reconnection in the tail current sheet can be responsible for triggering substorms and generating auroras. Recent observations have indicated that reconnection in the Martian tail enhances ion escape from the planet's atmosphere. However, the frequency of reconnection events in the Martian tail and their involvement in ion loss is still not fully understood based on previous few research. In this study, we use data from the Mars Atmosphere and Volatile EvolutioN spacecraft to study the Martian tail current sheet. For the first time, we find that almost 15% of the current sheet events on Mars have reconnection signatures, happening more often than on Earth. The high occurrence rate of magnetic reconnection at the Martian tail current sheet can be attributed to its extremely thin structure, which is on the scale of protons. Magnetic reconnection may drive high fluxes of hydrogen ions and thus potentially impact the evolution of the Martian atmosphere. MAVEN recorded 880 current sheet events in the Martian tail in the past 7 years and about 15% of them show reconnection featuresThe average thickness of the current sheet is on the proton scale and is thinner in the -E hemisphereThe reconnecting tail current sheet carries a higher net tailward flux of hydrogen ions