Soft X‐Ray Emission From Saturn's Magnetosheath Part I: 3D Modeling From MHD Data

Abstract Saturn's magnetosheath hosts a mixed population of water‐group neutrals and solar wind plasma. We present a 3‐D model of soft X‐ray emission by ion‐neutral charge exchange in the near‐equatorial magnetosheath. The model employs MHD simulation data of plasma properties at Saturn, Enceladus‐genic neutral populations extrapolated from existing physical chemistry models, and circumscribes the magnetosheath region using existing magnetopause and bow shock models. Emission is concentrated in the equatorial plane and toward the magnetosheath nose, with volumetric emission rates of 10 −10 –10 −11 photons cm −3 s −1 . We explore viable imaging distances for a SMILE‐like instrument. We conclude that imaging of Saturn's magnetopause is viable within 40 R S , with integration times on the order of ∼1 min. However, the SMILE SXI field of view would only image 0.5% of the emission region at this distance. Enhancements in effective area comparable to MIXS on BepiColombo or closer viewing with a wider field of view would enable the whole magnetosheath to be imaged on few‐minute timescales. Soft X‐ray emission observations can be used to study the location, structure, and global dynamics of the magnetosheath region, and to inform neutral density models, especially of the outer system. Finally, far viewing of the emission region as a point source may be sufficient to capture variability in emission rate driven both by Saturn's internal plasma environment and varying solar wind conditions.