Abstract/Summary

Interplanetary coronal mass ejections (ICMEs) are solar transients that have significant effects on the upper atmosphere and ionosphere of Mars. The simultaneous spacecraft observations from Tianwen1/MOMAG in solar wind and multiple instruments onboard the Mars Atmosphere and Volatile Evolution (MAVEN) in the Martian upper atmosphere are used to study the response of Mars to an ICME. The ICME was observed at Mars by Tianwen-1 and MAVEN at 00:00 UT on 10 December, 2021, which was earlier observed by BepiColombo upstream of Mars at 22:32 UT on 6 December, 2021. During 6–15 December 2021, MAVEN measured the nightside ionosphere and Tianwen-1 measured the dayside ionosphere while both were inside the Martian bow shock. The rapid drop in densities of ionospheric ions and electrons, which is typically identified as the end of the ionosphere at altitudes between 300 and 800 km, is known as ionopause. The altitude of the Martian ionopause location was lowered by the high dynamic pressure of solar wind during the ICME passage. The depletion of the plasma density in the topside Martian ionosphere on the nightside reveals the presence of substantial ion and electron escape to space through the interaction between the ICME and Mars. The column abundance of plasma dramatically decreased, with 34% e−, 61% O+2, and 73% O+ 36 reduced. This study highlights the significant impact of the space weather associated with the intense magnetic field and high dynamic pressure of the ICME on Mars’ atmosphere, which is particularly important for future human exploration missions to Mars.