Responses of the Martian Magnetosphere to Changes in the Solar Wind Velocity and the IMF Orientation

International audienceThe Mars Atmosphere and Volatile EvolutioN (MAVEN) mission is currently probing the very complex and dynamic Martian environment. Despite that main structures resulting from the interaction between the solar wind (SW) and the induced magnetosphere of Mars can be characterized using a steady state picture, time-dependent physical processes play a fudamental role modifying the reponse of such obstacle. These processes are the consequence of temporal variabilities in the internal and/or external electromagnetic fields and plasma properties. In this work we study the effects that changes in the IMF orientation and SW speed and the rotation of the crustal magnetic fields (CF) have on the Martian magnetosphere by means of MAVEN magnetic field and plasma measurements and LATMOS Hybrid Simulations (LatHyS) runs. Firstly, we analyze magnetic field and plasma measurements provided by MAVEN on 23 December 2014 between 06:00 UT and 14:20 UT. During this time interval the spacecraft sampled the Martian magnetosphere twice, with highly similar trajectories. MAVEN measurements suggest that the external conditions remained approximately constant when the spacecraft was inside the magnetosphere for the first time. In contrast, MAVEN observed changes in the IMF orientation before visiting the magnetosphere for the second time. Making use of the LatHyS model, we perform a time-dependent simulation to investigate the global response of the Martian plasma environment to the CF rotation and the change of the background magnetic field orientation, taking into account MAVEN observations to set the external conditions. Simulation results are compared with the MAVEN Magnetometer and Solar Wind Ion Analyzer observations obtained in the Martian magnetosphere and show a good agreement. Based on this agreement, we determine associated recovery timescales of the Martian magnetosphere to such event. Secondly, we perform LatHyS runs to characterize the response of the Martian magnetosphere to changes in the SW speed. Particularly, we investigate associated effects on the SW deflection taking place inside the Martian magnetosheath. Finally, we perform estimations of the total planetary proton and oxygen escape fluxes at different times during these events