Interaction of Space Weather Phenomena With Mars Plasma System During Solar Minimum 23/24

Abstract:

We study the interaction of three solar wind structures, two stream interaction regions and one interplanetary coronal mass ejection, with Mars' plasma environment during 20-27 November 2007. This period corresponds to the solar minimum between the solar cycles 23 and 24 which was characterized by very low values of the solar wind density and dynamic pressure and low IMF magnitude. Due to low solar photoionizing fluxes (EUV, X-ray), the ionosphere of Mars exhibited low ionization levels. During that time the Mars-Express orbit was in the terminator plane, while the Earth an Mars were almost aligned, so we use the ACE and STEREO probes as solar wind monitors in order to identify and characterize the structures that later hit Mars. We find that the passage of these structures caused strong variations of distance of the bow-shock (between 2.2 and 2.8 R_M), compression of the magnetospheric cavity (up to 54 %), increased mass outflow (up to ~10²⁵s^-1), changes in the outflow chemistry composition and an increased dusk-dawn asymmetry of the outflow. This study shows that during times of low solar activity, modest space weather phenomena may cause large variations of plasma escape fluxes from Mars.