The Response of the Martian Ion Precipitation to Extreme Solar Events

Ion precipitation is a major driver of sputtering on Mars, yet its behavior under extreme solar wind conditions remains poorly characterized. Using MAVEN observations, we analyze 124 extreme solar wind events from 2014 to 2018 together with a unique disappearing solar wind (DSW) interval. Precipitating ions are separated into low-energy (30–650 eV) and high-energy (650–25,000 eV) populations. Both statistical and event-specific analyses reveal a pronounced energy dependence. Low-energy precipitation increases with solar wind dynamic pressure but exhibits a two-stage response: an approximately linear rise at lower pressures followed by a markedly slower growth once a threshold pressure is exceeded. Low-energy precipitation flux also rises modestly with magnetic field strength and more steadily with Alfvén Mach number. In contrast, high-energy precipitation flux shows little correlation with upstream conditions, suggesting distinct sources or acceleration pathways during extreme events. The DSW case further demonstrates that a substantial decrease in dynamic pressure is accompanied by a pronounced reduction in low-energy precipitation flux, while high-energy precipitation flux remains comparatively unchanged. These results indicate that ion precipitation differs from responses reported under nominal solar wind conditions.