Entry and acceleration of He⁺ in the low latitude boundary layer

AMPTE/CCE He + and H + observations in the magnetosphere, low latitude boundary layer, and magnetosheath reveal that cold (∼tens of eV) plasmaspheric He + distributions from the outer magnetosphere convect into the low latitude boundary layer. In the boundary layer, the cold He + is accelerated and heated to a few keV. The data are resolved in sufficient detail to show that the process of pick up of the cold He + distribution in the boundary layer H + flow may not be adequate to explain the observed He + distributions in the boundary layer.