[P-PS05] Mars and martian moons

[PPS05-12] On the source of the quasi Carrington Rotation periodic magnetic variations on the Martian surface: InSight Observations and Modelling

*Hao Luo¹ (1.Institute of Geology and Geophysics, Chinese Academy of Sciences)

Keywords:InSight, Carringtion Rotation, Daily magnetic field variation

In a recent paper [Luo et al., 2022], we found that the daily peak amplitudes of the magnetic variations in a SOL at InSight landing site exhibited quasi Carrington-Rotation (qCR) period at higher eigenmodes of the natural orthogonal components (NOC) results for ~ 664 sols. However, the source of these periodic variations is still unknown. In this study, the neutral-wind driven ionospheric dynamo current model [e.g., Lillis et al., 2019] is introduced to investigate the source. Four candidates, the draped IMF, electron density/plasma density, the neutral densities, and the electron temperature in the ionosphere with artificial qCR periodicity, are applied in the modelling to find the main controlling factor for the resulting surface magnetic fields with the same qCR period. Results show that the electron density/plasma density, which controls the total conductivity in the dynamo region, accounts for the most part of the surface qCR variations, whose contribution reaches about 67.6%. The draped IMF, neutral densities, and the electron temperature account for only about 12.9%, 10.3%, and 9.2%, respectively. Our study implies that the magnetic field variations with qCR period on the Martian surface are mainly due to the variations of the corresponding dynamo currents and the variation of the electron density originates from anisotropic activities at the surface of the rotating Sun. It also implies that the time-varying fields with qCR period could be used to probe the Martian interior's electrical conductivity structure at least at a depth of 700 km.