Time Variation of Mars Atmospheric Loss in Response to Continuous Rotation of the Crustal Magnetic Field

Friday, 19 December 2014: 5:30 PM
Xiaohua Fang, University of Colorado at Boulder, Boulder, CO, United States and Yingjuan Ma, University of California Los Angeles, Los Angeles, CA, United States
Mars does not have a global intrinsic magnetic field but has localized crustal magnetic anomalies particularly in the southern hemisphere. Several studies have reported that heavy ion escape rates are highly dependent on the orientation of magnetic anomalies to the Sun, although significant uncertainty remains regarding the magnitude of the changes. Due to modeling complexity, however, all the previously published global studies were conducted based on an oversimplified steady state approximation. Very recently our team incorporated for the first time a time-dependent calculation into a global MHD model by considering the continuous rotation of the crustal field with the planet. The new non-steady-state simulations revealed a general anti-correlation of ion escape with the subsolar magnetic strength when the strongest crustal field region is on the dayside, consistent with previous findings. However, the details of how the rotation of the localized crustal field regulates global ion loss over time are still poorly understood, particularly when the strong magnetic anomalies move into the nightside. In contrast with previous global modeling work, which adopted a steady state approximation and mainly focused on the effects of external drivers (i.e., solar EUV and solar wind plasma), this study aims to improve our understanding of how the internal time-varying perturbation due to the rotation of crustal magnetic anomalies regulates the plasma interaction and ultimately affects planetary ion escape.