Modeling the Impact of a Strong X‐Class Solar Flare on the Planetary Ion Composition in Mercury's Magnetosphere

Abstract

The exosphere is maintained over time by different source and loss mechanisms. Mercury's exosphere is mainly sourced from the surface regolith, diffusion of gases from Mercury's interior and surface bombardment by solar wind ions (Killen et al., 2007). The species are released from the regolith into the exosphere by a variety of ejection processes, such as thermal desorption, photon-stimulated desorption, solar wind ion sputtering and meteoroid impact vapourization (Killen et al., 2007;Leblanc & Johnson, 2003. Neutrals are then lost from the exosphere by thermal (Jeans) escape, acceleration of the atoms by the solar radiation pressure to escape velocity and photoionization.Mercury has a small magnetosphere that is the result of the interaction between the interplanetary magnetic field (IMF) and the intrinsic dipole magnetic field (Anderson et al., 2011). The magnetospheric ion population mainly consists of solar wind ions, but planetary ions may contribute to as much as 10% of the total ion pressure (Yagi et al., 2010). The planetary ions that exist in Mercury's magnetosphere are primarily sourced from photoionization of the neutral exosphere. The Fast Imaging Plasma Spectrometer (FIPS;Andrews et al., 2007) onboard the Mercury Surface, Space Environment, Geochemistry, and Ranging (MESSENGER) spacecraft has mapped the distribution of planetary ions in Mercury's magnetosphere. Na + -group (mass-per charge ratio m/q = 21