The influence of crustal magnetic fields on the Martian bow shock : a statistical analysis of Mars Volatile EvolutioN and Mars Express observations

The Martian interaction with the solar wind is unique due to the influence of remanent crustal magnetic fields. The recent studies by the Mars Express and Mars Atmosphere and Volatile Evolution missions underline the strong and complex influence of the crustal magnetic fields on the Martian environment and its interaction with the solar wind. Among them is the influence on the dynamic plasma boundaries that shape this interaction and on the bow shock in particular.Compared to other drivers of the shock location (e.g. solar dynamic pressure, extreme ultraviolet fluxes), the influence of crustal magnetic fields are less understood, with essentially differences observed between the southern and northern hemispheres attributed to the crustal fields. In this presentation we analyze in detail the influence of the crustal fields on the Martian shock location by combining for the first time datasets from two different spacecraft (MAVEN/MEX). An application of machine learning techniques will also be used to increase the list of MAVEN shocks published to date. We show in particular the importance for analyzing biases due to multiple parameters of influence through a partial correlation approach. We also compare the impact of crustal fields with the other parameters of influence, and show that the main drivers of the shock location are by order of importance extreme ultraviolet fluxes and magnetosonic Mach number, crustal fields and then solar wind dynamic pressure.