Martian magnetic storms

The response of Mars to the major space weather events called interplanetary coronal mass ejections (ICMEs) is of interest for both general planetary solar wind interaction studies and related speculations on their evolutionary consequenc-esespecially with respect to atmosphere escape. Various particle and field signatures of ICMEs have been observed on Phobos-2, Mars Global Surveyor (MGS), Mars Express (MEX), and now Mars Atmosphere and Volatile EvolutioN (MAVEN). Of these, MAVEN's combined instrumentation and orbit geometry is particularly well suited to characterize both the event drivers and their consequences. However, MAVEN has detected only moderate disturbances at Mars due in large part to the general weakness of the present solar cycle. Nevertheless, the strongest event observed by MAVEN in March 2015 provides an example illustrating how further insights can be gained from available models. Here we first look more closely at what previously run BATS-R-US MHD simulations of the combined MAVEN observations tell us about the March 2015 event consequences. We then use analogous models to infer those same responses, including magnetic field topology changes and ionospheric consequences, to a hypothetical extreme ICME at Mars based on STEREO A measurements in July 2012. The results suggest how greatly enhanced, yet realistic, solar wind pressure, magnetic field, and convection electric field combine to produce strong magnetospheric coupling with important consequences for upper atmosphere and ionosphere energization.