Statistical differences in the properties of the Martian foreshock boundary during selected high and low solar activity intervals

As the primary transition region in the solar wind–Mars interaction system, the Martian foreshock plays a significant role in the energy transfer and dissipation of the solar wind. Based on MAVEN (Mars Atmosphere and Volatile Evolution) observations during the selected solar high-activity interval from December 2014 to February 2015 and solar low-activity interval from December 2018 to February 2019, the properties of the Martian foreshock boundary are statistically studied. Distributions of solar wind parameters, including the density, velocity, dynamic pressure, and magnetic field strength, are investigated for analyses of their differences across the Martian foreshock boundary. Our results indicate that solar wind velocity across the Martian foreshock boundary shows little variation with respect to the solar activity levels. The solar wind dynamic pressure decreases slightly less during the selected low-activity interval, whereas the solar wind density shows a stronger enhancement during the selected low-activity interval. The boundary of the Martian foreshock is located farther from the bow shock during the selected high-activity interval and exhibits systematic correlations with the solar wind velocity and density. These findings support the interpretation that the structure and dynamics of the Martian foreshock are different between the selected solar high- and low-activity intervals, which is important for improved understanding of the cross-scale interactions between the solar wind and Martian space.