Solar wind charge exchange X-ray emission from Mars Model and data comparison

TL;DR

This study models the soft X-ray emission from Mars caused by charge exchange between solar wind ions and the Martian exosphere, comparing simulations with XMM-Newton observations to understand planetary-solar wind interactions.

Contribution

The paper introduces a 3D hybrid simulation combined with a test-particle model to accurately predict X-ray emissions from Mars and compares these with actual observations.

Findings

Simulated X-ray maps reflect Martian electromagnetic structure.

Discrepancies found between model predictions and observed luminosity.

Model cannot fully reproduce the high luminosity observed by XMM-Newton.

Abstract

Aims. We study the soft X-ray emission induced by charge exchange (CX) collisions between solar-wind, highly charged ions and neutral atoms of the Martian exosphere. Methods. A 3D multi species hybrid simulation model with improved spatial resolution (130 km) is used to describe the interaction between the solar wind and the Martian neutrals. We calculated velocity and density distributions of the solar wind plasma in the Martian environment with realistic planetary ions description, using spherically symmetric exospheric H and O profiles. Following that, a 3D test-particle model was developed to compute the X-ray emission produced by CX collisions between neutrals and solar wind minor ions. The model results are compared to XMM-Newton observations of Mars. Results. We calculate projected X-ray emission maps for the XMM-Newton observing conditions and demonstrate how the X-ray emission reflects the Martian electromagnetic structure in accordance with the observed X-ray images. Our maps confirm that X-ray images are a powerful tool for the study of solar wind - planetary interfaces. However, the simulation results reveal several quantitative discrepancies compared to the observations. Typical solar wind and neutral coronae conditions corresponding to the 2003 observation period of Mars cannot reproduce the high luminosity or the corresponding very extended halo observed with XMM-Newton. Potential explanations of these discrepancies are discussed.