In Situ Observations of Whistler-mode Waves in Magnetic Reconnection at Mars

Whistler-mode waves are one of the most important plasma waves potentially affecting the triggering and development processes of magnetic reconnection. They are widely present in the Earth’s reconnection ion diffusion region but have not yet been reported in Mars’. Based on in situ measurements from MAVEN, the Mars Atmosphere and Volatile Evolution mission, we report for the first time whistler-mode waves in the ion diffusion region at the center of the current sheet in the Martian magnetotail. Simultaneously, pancake electron distributions with high temperature anisotropy are observed. Linear instability analyses imply that these unstable electrons can trigger the observed whistler-mode waves. Such findings not only fill the gap in observations of whistler-mode waves in the magnetic reconnection at Mars but also enrich our understanding of their generation mechanism in the reconnection region at unmagnetized planets.