Alteration of Magnetic Field Strength in the Strong Crustal Field Region at Mars by Currents Induced by the Solar Wind Interaction. Issue 4 (28th March 2023)

• Record Type: Journal Article
• Authors: Renzaglia, A.; Cravens, T. E.; Hamil, O.
• Is Part Of: Journal of geophysical research. Volume 128:Issue 4(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2023-03-28
• Subjects: Mars ionosphere -- planetary atmospheres -- MAVEN data -- magnetic fields -- Martian crustal fields -- Mars‐solar wind interaction; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1029/2022JA030487
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: Crustal 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. Plain Language Summary: Crustal fields are magnetic fields that are produced in the Martian crust and extend into and above the atmosphere. These fields are thought to play a role in atmosphere loss from Mars. The crustal fields change over billions of years but are unchanged over the course of this work. There have been many models created to try and map out these fields on Mars. Alternatively, induced magnetic fields are generated from the interaction between Mars and the solar wind. The induced fields do vary substantially over local time (particularly daytime vs. nighttime). We look at the boundary between these two types of magnetic fields, using data from the Mars Atmospheric and Volatile EvolutioN (MAVEN) spacecraft. We compare differences between MAVEN data and predicted crustal field model values, then compare these differences between two orbits—one dayside and one nightside—that pass over the same region of Mars. We also compare dayside cases, for different local times. We find that dayside orbits have larger differences between model and data, and the closer to noon, the larger the difference. We aim to understand the interaction between induced and crustal fields and speculate how this could affect atmospheric loss from Mars. Key Points: Mars Atmospheric and Volatile EvolutioN magnetometer data shows deviation from crustal models. Commonly, larger deviations are seen on the dayside rather than on the nightside Typical dayside deviations are about 20 nT, but vary with solar zenith angle Ionospheric currents induced by the solar wind interaction with Mars can in part explain the deviations seen