The Mixture of Mirror-mode and EMIC Waves in the Martian Magnetosheath: MAVEN Observations

Electromagnetic Ion Cyclotron (EMIC) waves and Mirror-Mode (MM) waves, ubiquitously observed in terrestrial and interplanetary space, usually are found to compete and hardly occur simultaneously. In this letter, we first present observations of MM and EMIC wave mixture in the Martian magnetosheath by MAVEN and Tianwen-1. We present two mixed events, one with locally excited EMIC waves and one without, and discuss the excitation conditions of EMIC and MM waves. The results suggest that the two waves can be simultaneously excited under moderate plasma β and ion temperature anisotropy, which aligns with the outcomes of our quasi-linear theory calculations. We also found that the combined effect of ion pickup processes on Mars and quasi-parallel shock compression may have provided the moderate plasma conditions required. This study may shed new light on the generation mechanisms of MM and EMIC and their interaction with particles.