講演情報
[PPS07-P11]Impact of Martian Crustal Magnetic Fields on the Non-thermal Escape of Hot Oxygen and Heavy Ions
*Hua-Shan Shih1、Jih-Hong Shue1、Wing-Huen Ip1,2 (1.Department of Space Science & Engineering, National Central University, Taiwan、2. Institute of Astronomy, National Central University, Taiwan)
キーワード：
Mars、Martian Magnetosphere、Monte Carlo methods、Magnetohydrodynamics
The atmospheric escape process is a fundamental mechanism driving the long-term evolution of the Martian climate and atmosphere. Lacking a global dipole magnetic field, the structure of the Martian upper atmosphere and ionosphere is significantly influenced by the interplay between the solar wind, the Interplanetary Magnetic Field (IMF), and local crustal magnetic fields. Among these processes, non-thermal escape plays an important role in atmospheric loss; in particular, the escape of hot oxygen and heavy ions has a substantial impact on the structure and dynamics of the upper atmosphere. In this study, we systematically analyze the effects of crustal magnetic fields and the induced magnetosphere structure on non-thermal atmospheric escape by combining a three-dimensional test-particle Monte Carlo simulation with a multi-fluid magnetohydrodynamic (MHD) model. We first investigate the modulation effects of crustal magnetic fields on hot oxygen dynamics and escape rates. Furthermore, using the altitude of the Induced Magnetosphere Boundary (IMB) as a proxy for disturbed and compressed conditions, we analyze the variations in ion escape behavior under different magnetic field configurations. Simulation results indicate that the inclusion of crustal magnetic fields increases the total hot oxygen escape rate by approximately 23% compared to the unmagnetized case. In the southern hemisphere, where crustal fields are concentrated, local hot oxygen escape rates can increase. This significant hemispheric asymmetry arises primarily from plasma transport processes controlled by local magnetic topology and electromagnetic forces—specifically the Hall electric force. These mechanisms lead to a reorganization of ion and electron spatial density distributions, as well as ion acceleration and guidance along magnetic field lines, thereby enhancing hot oxygen escape efficiency in strong-field regions. Additionally, we examine the impact of the induced magnetosphere structure on heavy ion escape efficiency by comparing oxygen ion escape fluxes and spatial distributions under varying IMB altitudes. To more accurately characterize ion acceleration and escape channels in low-altitude regions, we perform backward trajectory tracing based on numerical simulation results, further elucidating the respective roles of crustal and induced magnetic fields in the heavy ion escape process.