Mars Express observations of the stretch effect of mini-magnetospheres formed by crustal fields on the Martian bow shock location

The strong crustal magnetic fields significantly alter the structure of the Martian space environment, including all plasma boundaries. The stretches of mini-magnetospheres formed by crustal fields from the location of the Martian bow shocks were first found from the Mars Atmosphere and Volatile EvolutioN (MAVEN) observations. The present study aims to test whether this effect is also present in the shocks observed by Mars Express (MEX). We find that the bow shocks above the crustal field regions are enlarged, resulting in a north−south asymmetry and a longitude dependence in the shock size. The longitude dependence is more pronounced for near-subsolar shocks, and more dispersed for near-terminator shocks. The enlarged shocks are also observed to have shifted tailward from the longitudes of the strongest crustal fields. Due to a dawnside bias in MEX shock crossings, the enlarged shocks generally display a westward shift from the strongest crustal field region. These results confirm that stretches of the mini-magnetosphere are also present in the MEX shock observations.