Magnetospheric Solar Wind Charge Exchange – A Comparison Between the GUMICS-4 MHD Model and XMM-Newton.

Abstract:

The Solar Wind Earth Exchange Project (SWEEP) seeks to improve our understanding of the interaction of the solar wind with the Earth. X-ray emission resulting from charge exchange between oxygen in the solar wind and magnetospheric neutral hydrogen is modelled for a series of observations from XMM-Newton, an X-ray astronomical observatory. We use OMNI solar wind conditions, heavy ion composition data from ACE, the Hodges neutral hydrogen model and combine these with the GUMICS-4 MHD model to predict the global levels of X-ray emission from solar wind charge exchange (in the 0.5-0.7 keV band). The emission is then integrated along a line of sight and compared to the measured XMM-Newton sky background emissivity rates to determine the accuracy of these model predictions. Our results show that the magnitude of the integrated X-ray emissivity for both the modelled and observed flux is similar in a large number of cases, while the correlation of emission changes in detail between cases. We show that the accuracy of the oxygen density and relative charge state abundances is vital. The positional accuracy of the magnetopause is important as it forms the outer edge of the masking of the plasmasphere, including the cusps in our global emissivity rates. The derived position of the magnetopause and various masks are discussed with examples given, highlighting their relative accuracy. We also show the potential of X-ray emission for remote sensing of the magnetosphere, when used in combination with a wide field X-ray imaging system.