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

We study the interaction of three solar wind (SW) structures, two stream interaction regions, and one interplanetary coronal mass ejection, with Mars’ plasma environment during November 20–27, 2007. This period corresponds to the solar minimum between the solar cycles 23 and 24 which was characterized by very low values of the SW density and dynamic pressure and low interplanetary magnetic field magnitude. During that time the Mars Express orbit was in the terminator plane, while the Earth, Sun, and Mars were almost aligned, so we use the Advance Composition Explorer and Solar Terrestrial Relations Observatory probes as SW monitors in order to identify and characterize the structures that later hit Mars. We find that the passage of these structures caused strong variations in the bow shock location (between 2.2 and 3.0 RM), compression of the magnetospheric cavity (up to 45%), and an increased transterminator flow below 2 RM (by a factor of ≤ 8). This study shows that during times of low solar activity, modest space weather phenomena may cause large variations of plasma flow at Mars.

Plain Language Summary

Unlike Earth, Mars does not possess a global magnetic field. Instead it is its ionosphere that represents the obstacle for the solar wind (SW) and thus the induced magnetosphere, magnetosheath, and the bow shock are formed. We make use of the fact that in November 2007, so during the solar minimum 23/24, Mars Express orbit laid in a terminator plane, which made it possible to study transterminator planetary plasma flow. During November 20–27, 2007 Mars interacted with two stream interaction regions and one interplanetary coronal mass ejection. All of these phenomena were of moderate intensity. We know this since at the time Mars and Earth were aligned, so we are able to use Advance Composition Explorer, Solar Terrestrial Relations Observatory (STEREO A), and STEREO B spacecraft as solar monitors. We show that during solar minima moderate SW structures may cause large planetary transterminator flows. These also show variations of their chemistry compositions.