The response of the Venusian upper atmosphere during the passage of interplanetary coronal mass ejections

The study explores the dynamic interaction between Interplanetary coronal mass ejections (ICMEs) and the induced magnetosphere of Venus, utilizing measurements from the Venus Express (VEX) mission. Over the period 2006-2013, we analyzed 16 ICME events, noting peak magnetic field strengths at the ionopause around 100 nT. Our investigation comprehensively examines the altitude of the inbound bow shock and ionopause during these ICME passages. The ionosphere is found to be highly magnetized due to the very high magnetic pressure of the induced magnetosphere.  Remarkably, the altitude of the ionopause is found to be significantly compressed as compared to the previous quiet day due to the increased solar wind dynamic pressure. Intriguingly, the bow shock position exhibited minimal deviations compared to typical quiet days, underscoring that, during ICME events, the ionopause location is more responsive to solar wind pressure fluctuations than the bow shock location. Additionally, we observed a notable increase in heavy-ion density near and above the ionopause compared to quiet days. This substantial increase implies that ICMEs can induce atmospheric loss in Venus’s atmosphere and also cause a significant reduction in the ionopause location.