Statistical properties of hot flow anomalies around Mars

Hot flow anomalies (HFAs) are not only a terrestrial phenomenon, but also a solar-system-wide phenomenon, one that can cause significant perturbations in planetary magnetospheres and ionospheres. In this study, based on the observations of Mars Atmosphere and Volatile EvolutioN (MAVEN) mission in the region upstream of the Martian bow shock from the year 2014 to 2020, we have investigated the statistical properties of HFAs around Mars. Our results show that HFAs can be found in a wide region of Mars, from the dayside to the terminator region. On average, these HFAs last 63 seconds, with a thickness of 28 local proton gyroradii. They are more prevalent when the ambient solar wind is denser and faster, and usually occur when the interplanetary magnetic field magnitude is between 1−4 nT. Martian HFAs can also lead to solar wind dynamics multiplying in pressure by factors of ten within only tens of seconds, which could significantly influence the heights of the Martian ionopause and induced magnetosphere boundary. By comparing HFAs around Earth, we suggest that these phenomena are primarily governed by solar wind dynamics rather than local planetary conditions.