Induced Magnetic Field Distribution and Variability at Mars: MHD Prediction and Comparison with MAVEN Observations

Mars has no strong intrinsic dipole field but has locally concentrated and globally spread crustal magnetic field anomalies. The interaction of Mars with the impinging solar wind and interplanetary magnetic field (IMF) results in a complex magnetosphere, which not only exhibits the characteristics of a Venus-like induced magnetosphere but also is subject to the control of locally-dominant crustal fields particularly at low altitudes. The magnetic field at Mars is composed of the intrinsic crustal field and the induced field, the latter of which is produced by electric currents that are induced from the complex solar wind-Mars interaction. Despite that numerous empirical models have been developed to describe the crustal field distribution in the planetary reference frame, the global distribution of the induced field and its variability are not well understood. Most of the complexity comes from the fact that the planet-attached crustal field continuously rotates and changes its orientation to the Sun, but the induced field is more organized in the Sun-Mars reference frame than in the planetary frame. In this work, we will apply a 3-D time-dependent magnetohydrodynamic (MHD) model to self-consistently solve plasma and field interaction over the course of planetary rotation during representative seasons and under typical Parker spiral IMF polarities. The model results enable us to derive a global view of how the induced field is globally distributed and is altered by local crustal fields. Our findings will be compared with statistical results from Mars Atmosphere and Volatile EvolutioN (MAVEN) observations.