On the Origin of the Upstream Diffuse Ions: Case Studies from GEOTAIL Observations

Abstract

GEOTAIL observation in the distant dusk upstream region showed the existence of the diffuse upstream ions (5-43 keV/q) when the interplanetary magnetic field was nearly radial and separated from the nearest magnetopause by >20-30 RE. Since even with the Bohm limit the perpendicular diffusion was not fast enough to transport the magnetospheric ions to the spacecraft, we conclude that these diffuse ions had a bow shock origin.