Alteration of Magnetic Field Strength in the Strong Crustal Field Region at Mars by Currents Induced by the Solar Wind Interaction

Abstract

AbstractCrustal magnetic fields on Mars were first found by the Mars Global Surveyor and reported in 1998. One interesting aspect of the interaction between crustal fields and the Martian ionosphere is the impact on total ion loss over time, which is a central question addressed by the Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft currently orbiting Mars. In this work, we seek to improve understanding of the impact of crustal fields on plasma energetics, and consequent ion loss, by examining the effects of ionospheric current sheets that may form at the boundary between crustal and induced magnetic fields. These current sheets will not just affect the external induced field regions but will also affect the observed magnetic fields in the crustal field regions. Variations in field strength should be evident by comparing crustal field models and measured magnetic fields collected by the MAVEN magnetometer instrument (MAG). One way to confirm such variation is to compare dayside and nightside orbit pairs that occur over the same crustal field regions. The induced magnetic field exists mostly on the dayside and is largely absent on the nightside. We examine these orbit pairs and discuss the perturbation of magnetic fields in the dayside ionosphere. We confirm that deviations on the dayside are larger than on the nightside, and that current sheets in the ionosphere could be responsible for these deviations, particularly in the strong crustal field regions.