Resolving Magnetosheath Jet Responses in Soft X-ray Images

Abstract

Magnetosheath jets are plasma structures within the magnetosheath of enhanced dynamic pressure which can impact the magnetopause and influence magnetospheric dynamics. The enhanced plasma flux within the jets are expected to result in enhanced soft X-ray emissions through the solar wind charge exchange mechanism due to greater collision rates with neutral hydrogen atoms. In this paper, we simulate magnetosheath jets and model realistic soft X-ray count maps to determine the size of telescope required to resolve them. We use the soft X-ray imager on the Solar wind Magnetosphere Ionosphere Link Explorer (SMILE-SXI) as our reference telescope. We show using realistic hybrid-based simulations that if multiple jets are present along the line of sight, it is difficult to resolve them in line of sight integrated intensity maps. Assuming only a single jet is present, we devise a Poisson means based test to determine if a jet can be resolved from the surrounding magnetosheath in an SXI image. From this, we determine that both a strong contrast between the jet and surrounding magnetosheath, and a minimum number of X-ray counts are required to resolve the jet. The foreground emission must also dominate the astrophysical background emission, which requires strong solar wind driving. Whilst resolving jets is unlikely for SMILE-SXI, it is possible to resolve a single jet from the right viewing angle with a larger telescope that is feasible to build. We comment on how this might be done.