Abstract The soft X‐ray imager (SXI) on the SMILE mission promises to revolutionize our understanding of the magnetopause by observing solar wind charge exchange emission from the magnetosheath on a global scale. The primary goal of this instrument is to infer the position and shape of the magnetopause from these images. One method involves devising a 3D X‐ray emissions model through which an image can be simulated and adjusted to match a real image. The magnetopause position can be extracted from the fitted 3D model. Previous work by Wharton et al. (2025b), https://doi.org/10.1029/2025ja033837 showed this method was effective with noisy SXI images if solar wind data was used to initialize their Cusp and Magnetosheath Emissivity Model (CMEM1). This study develops CMEM2, a constrained and simplified model that does not require solar wind data for initialization but uses information in the image instead. It can also be fitted by a range of fitting algorithms, which we thoroughly compare. CMEM2 is shown to perform as accurately as CMEM1. We also test this method for the first time on realistic scenarios with changing solar wind conditions. We find the method struggles during median solar wind conditions when the magnetosheath is dim and largely out of the expected FOV of SMILE‐SXI. However, during active conditions, the method tracks the movement of the magnetopause well and produces errors within the 0.5 requirement for the SMILE mission, providing that the initialization of CMEM2 is reasonably accurate.
Wharton et al. (Thu,) studied this question.