Statistical study of non-adiabatic energization and transport in Kelvin-Helmholtz vortices 2 at Mercury Key words: Mercury's magnetosphere, Kelvin-Helmholtz instability, particle
Résumé
Non-adiabatic energization and transport of planetary ions in the vicinity of Kelvin-Helmholtz (KH) vortices at Mercury are statistically investigated using a magnetohydrodynamic model combined with a test particle tracing technique. The measurements from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft show the signature of KH waves in the magnetospheric flanks, especially on the duskside. We examine here the energization and transport of heavy ions of planetary origin such as associated with the growth of the KH instability on both the dawn and dusk sides Na+ of the magnetosphere, and for both northward and southward interplanetary magnetic field configurations. We find that in all cases picked up planetary ions in the magnetosphere can be accelerated non-adiabatically with a level of acceleration larger on the dawnside. The transport of ions is controlled by the convection electric field in the magnetosheath. The planetary ions picked up in the duskside magnetosphere stagnate inside the magnetosphere where the KH waves have been mainly observed at Mercury and, hence, are not expected to escape. The present study indicates that these energized ions may likely stay inside the magnetosphere and sputter the planetary surface on the duskside preferentially, being the source of secondary neutrals from the planetary surface.
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