Van Allen Probes Observations of Oxygen Ions at the Geospace Plume

The geospace plume couples the ionosphere, plasmasphere, and magnetosphere from sub-auroral regions to magnetopause, on polar field lines, into magnetotail. We describe Van Allen Probes observations of ionospheric O+ ions at altitudes 3–6 R E in near vicinity noon post-noon sector. temporal variation warm ion fluxes observed as a function time moving spacecraft is complicated by changing position complex drift paths velocities that are highly sensitive energy, pitch angle L value. In “notch” region lower density plasma outside morning-side plasmapause, bi-directionally aligned energy (<5 keV) ions, following corotation-dominated trajectories midnight sector, excluded lines they deflected sunward flow channel. general, ring current energies (∼10 while O + (<3 absent. observation plumes with increasing ∼1 keV–>20 keV dusk sector outer plasmasphere interpreted evidence for localized outflow edge subsequent acceleration >50 <30 min during ions’ drift.