Global hybrid simulations of soft X-ray emissions in the Earth’s magnetosheath
Jin Guo, Tianran Sun, San Lu, Quanming Lu, Yu Lin, Xueyi Wang, Chi Wang, Rongsheng Wang, Kai Huang
Abstract
Earth’s magnetopause is a thin boundary separating the shocked solar wind plasma from the magnetospheric plasmas, and it is also the boundary of the solar wind energy transport to the magnetosphere. Soft X-ray imaging allows investigation of the large-scale magnetopause by providing a two-dimensional (2-D) global view from a satellite. By performing 3-D global hybrid-particle-in-cell (hybrid-PIC) simulations, we obtain the soft X-ray imaging of Earth’s magnetopause under different solar wind conditions, such as different plasma densities and directions of southward interplanetary magnetic field. In all cases, the magnetic reconnection occurs at low latitude magnetopause. The soft X-ray images observed by a hypothetical satellite are shown, and the boundary of the magnetopause, the cusps, and the magnetosheath are all identified in the X-ray images. There is a large amplitude fluctuation of the local X-ray emissivity (up to 160%) in the magnetosheath. However, the maximum line-of-sight-integrated X-ray intensity matches the tangent directions of the magnetopause well, which indicates that the influence of magnetosheath fluctuations on identifying magnetopause boundary in the X-ray image is limited. Moreover, the magnetopause boundary can be identified with different viewing geometries. We also find that solar wind conditions have little effect on the magnetopause identification. The Solar wind Magnetosphere Ionosphere Link Explorer (SMILE) mission will provide the X-ray images of the magnetopause for the first time, and our global hybrid-PIC simulation results can help better understand the 2-D X-ray images of the magnetopause from a 3-D perspective, with particle kinetic effects considered.