The response of the Venusian plasma environment to the passage of an ICME: hybrid simulation results and Venus Express observations

Owing to the heritage of previous missions such as the Pioneer Venus Orbiter and Venus Express (VEX), the typical global plasma environment of Venus is relatively well understood. On the other hand, this is not true for more extreme driving conditions such as during passages of Interplanetary Coronal Mass Ejections (ICMEs). Some of the outstanding questions are how do ICMEs, either the ejecta or sheath portions, impact: 1) the Venusian magnetic topology, and 2) escape rates of planetary ions? One of the main issues encountered when addressing these problems is the difficulty of inferring global dynamics from single spacecraft obits; this is where the benefits of simulations become apparent. In the present study, we present a detailed case study of an ICME interaction with Venus on 05 November 2011 in which the magnetic barrier reached over 250 nT. We use both VEX observations and hybrid simulation runs to study the impact on the field draping pattern and the escape rates of planetary O+ ions. The simulation showed that the magnetic field line draping pattern around Venus during the ICME is similar to that during typical solar wind conditions and that O+ ion escape rates are increased by approximately 30% due to the ICME. Moreover, the atypically large magnetic barrier appears to manifest from a number of factors such as the flux pile up, day-side compression, and the driving time from the ICME ejecta.