Journal Article

Mars Nightside Ionospheric Response During the Disappearing Solar Wind Event: First Results

Rout, D., Ram, L., Sarkhel, S.

2024

Overview

We investigated, for the first time, the impact of the disappearing solar wind (DSW) event [26–28 December 2022] on the deep nightside ionospheric species using MAVEN data sets. An enhanced plasma density has been observed in the Martian nightside ionosphere during extreme low solar wind density and pressure periods. At a given altitude, the electron density surged by ∼2.5 times, while for ions (NO+, O2+, CO2+, C+, N+, O+, and OH+), it enhanced by > 10 times, respectively, compared to their typical average quiet‐time periods. This investigation suggests that an upward ionospheric expansion likely took place in a direct consequence to the contrasting low dynamic/magnetic pressure and relatively higher nightside ionospheric pressure (by 1–2 orders) causing an increased ionospheric density. Moreover, the day‐to‐night plasma transport may also be a contributing factor to the increased plasma density. Thus, this study offers a new insight about planetary atmosphere/ionosphere during extreme quiescent solar wind periods. Plain Language Summary The evolution of the Mars climate over time depends upon the solar wind‐Mars interactions. The varying activity over the Sun intermittently produce extreme low density solar wind or also called as disappearing Solar Wind (DSW), which can affect the planetary environment in many ways. Beyond Earth, the effect of DSW on other planetary atmospheres is not well studied. In order to understand this aspect, we have explored the behavior of Martian nightside plasma environment (species: e−, NO+, O2+, CO2+, C+, N+, O+, and OH+) during the DSW event. A dense ionosphere is observed during DSW compared to non‐DSW periods. During DSW, the magnitude of peak nightside electron and ions density are increased by ∼2.5 and more than 10 times, respectively compared to their typical average quiet‐time scenario. The higher plasma density could be due to an expansion from the lower to the topside ionosphere, in consequence to the higher ionospheric pressure as compared to the low solar wind pressure. Furthermore, it could also be enhanced by the transport of plasma from dayside to nightside. Hence, this study, for the first instance, guides us to a new understanding of the impact of a rarest solar wind phenomenon on the Martian ionosphere. Key Points An increased plasma density is observed in the nightside ionosphere during the disappearing solar wind periods around Mars The electron and ions abundance surged by a factor of ∼2.5 and >10 respectively, compared to the average quiet‐time periods The contrast between the higher nightside ionospheric pressure and the dynamic/magnetosheath pressure led to increased plasma densities

• Publisher: John Wiley & Sons, Inc,Wiley
• Subject: Carbon dioxide / Cobalt / disappearing solar wind (DSW) / Electron density / Ionosphere / Ions / Mars / Mars atmosphere / Mars climate / Mars ionosphere / Mars‐solar wind interaction / Martian nightside ionosphere / MAVEN / Planetary atmospheres / Planetary environments / Planetary evolution / Planetary ionospheres / Plasma / Plasma density / Pressure / Solar wind / Solar wind density / Solar wind pressures / Wind pressure