Impact of solar wind disappearance event on the Martian nightside ionospheric species: First results

Abstract

The impact of a rarest solar wind phenomenon [disappearing solar wind (DSW) event during 26-28 December 2022] on the Martian nightside ionosphere is investigated, for the first time, using MAVEN datasets. During an extremely low solar wind density, the Martian top nightside ionospheric species underwent significant enhancements. At a given altitude, the density of electron increased by ~2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it increased by >10 times, respectively, compared to their typical average quiet-time periods. The extremely low dynamic pressure during the DSW event, contrasting with relatively higher nightside ionospheric thermal pressure nearly by an order, suggests an upward ionospheric expansion as a direct consequence. This causes an increased topside ionospheric density. Additionally, the day-to-night plasma transport may also be a contributing factor to increased plasma density. Thus, this study presents a new insight about planetary atmosphere/ionosphere response to the rarest event.