Ion Loss within a Reconnection Exhaust near Mars: MAVEN Observations

We present observations from Mars Atmosphere and Volatile EvolutioN of a reconnection exhaust, which was probably not ongoing, in the Martian magnetosheath. The reconnection jet with abundant heavy ions is directed outward to space. The magnetic field lines within the exhaust are found to be draped, suggesting that the reconnection exhaust was detached from the ionosphere and the heavy ions within it escaped from Mars. The dimensionless reconnection rate estimated from proton measurements is about 5.56%. The total oxygen loss rate via the reconnection exhaust is calculated to be 1.3 × 10 21 s −1 . This much lower ion loss rate than that estimated in active magnetic reconnection at the ionopause suggests that the reconnection associated with the reconnection exhaust is not ongoing, so most of the heavy ions have already escaped. Our results demonstrate that magnetic reconnection can directly contribute to the ion loss of Mars. Due to the participation of multiple heavy ions, the characteristics of magnetic reconnection could be very different.