Observations of nearly coincident induced magnetopause and ionopause at Venus

Using observations from the Venus Express (VEX), we reported the nearly coincident induced magnetopause (IMP) and ionopause structure on Venus. Throughout the VEX mission, we identified 31 coincident events and detailed three distinct types of events on November 26, 2011, January 15, 2014, and November 5, 2011. Our findings indicate that the coincidence of IMP and ionopause is influenced by the massloading effect, which depends primarily on the escaping ion flux from the planet and the conventional electric field of the solar wind. On November 26, 2011, the escaping ion flux from Venus was low. On January 15, 2014, the convection electric field of the solar wind was weak due to the small cone angle of the interplanetary magnetic field (IMF). Consequently, the massloading was insufficient to anchor the IMF, causing the IMP to be very close to the ionopause. On November 5, 2011, a strong interplanetary coronal mass ejection with a very intense magnetic field passed over Venus. Despite the strong massloading effect, the IMP was pushed low enough to be close to the ionopause. These observations suggest that the dayside induced magnetosphere of Venus, with its outer boundary at the IMP and inner boundary at the ionopause, can be very thin.