By Ardra Ramachandran (University of Warwick)
Solar wind charge exchange (SWCX) is a process in which X-rays are produced when heavy ions in the solar wind interact with neutrals in the solar system. Earth has a neutral hydrogen exosphere; when solar wind heavy ions interact with this hydrogen, they produce soft X-rays in the range of 0.1–2 keV. Earth’s magnetosphere acts as a shield that prevents the solar wind from penetrating further, making these X-rays a useful way to trace magnetospheric boundaries, including the magnetopause and cusps.
This study discusses the new Gorgon-XIM model, which combines magnetohydrodynamics (MHD) with a test-particle model to simulate SWCX X-rays from Earth’s magnetospheric boundaries. We compare XIM simulations with pure MHD simulations, which are less computationally expensive and treat magnetospheric plasma as a single fluid. We also discuss the line-of-sight (LOS) images and spectra produced by XIM, which enable us to compare the model with observations from space-based X-ray observatories of the magnetosphere, such as the newly launched SMILE mission. We conclude that XIM captures particle kinetic effects and the dependence of SWCX on heavy-ion species, which are not represented in the MHD model. Variations in the X-ray spectra can also be used to diagnose plasma dynamics and distinguish between different types of solar wind.
See publication for more details:
https://doi.org/10.48550/arXiv.2609.35098

Line-of-sight (LOS)-integrated SWCX emission maps. Panels (a)–(c) show the results for Mg¹¹⁺, C⁵⁺, and the MHD-only emission for C⁵⁺, respectively, for a satellite at (−10 Rₑ, 0 Rₑ, 10 Rₑ). The red box in these panels represents the SMILE field of view (FOV) for reference. Panels (d)–(f) show the corresponding results for a satellite at (−10 Rₑ, 10 Rₑ, 0 Rₑ). Both cases look toward (−10 Rₑ, 0 Rₑ, 0 Rₑ).