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Abstract

The Earth’s magnetosheath is populated by plasma irregularities of finite spatial extent that propagate in the antisunward direction and interact with the magnetopause. These structures, known as high-speed plasma jets, are characterized by an excess of density and velocity with respect to the background environment. Their dynamics prior, during and after the interaction with the magnetopause is still not fully understood. In the present paper we investigate the soft X-ray signatures associated with the high-speed magnetosheath jets streaming towards the dayside magnetopause. For this purpose, we use a kinematic approach based on magnetohydrodynamic (MHD) simulations and theoretical insight from particle-in-cell (PIC) simulations and Vlasov modelling. The background state of the magnetosphere is obtained from global MHD simulations, while the high-speed plasma jets are considered as local perturbations superposed onto the background state. By knowing the physical parameters of the total (background + jet) plasma system, we compute the volume emission rate of the soft X-rays generated by the interaction between the high-charge state solar wind ions and the terrestrial exospheric hydrogen through the solar wind charge exchange (SWCX) process. The soft X-ray intensity is further calculated by integrating the volume emission rate along the line-of-sight from a virtual spacecraft launched into the simulation domain. The virtual spacecraft simulates the Soft X-ray Imager (SXI) on-board the Solar wind-Magnetosphere-Ionosphere Link Explorer (SMILE) mission to be launched in late 2024. By running multiple simulation scenarios under various conditions, we estimate the observability potential of the high-speed magnetosheath jets by SMILE SXI.