Abstract
AbstractThe ion plasma sheet (~few hundred eV to ~few tens keV) is usually dominated by H+ ions. Here changes in ion composition within the plasma sheet are explored both during individual events and statistically during 54 calm‐to‐storm events and during 21 active‐to‐calm events. Ion composition data from the HOPE (Helium, Oxygen, Proton, Electron) instruments onboard Van Allen Probes satellites provide exceptional spatial resolution and temporal resolution of the H+, O+, and He+ ion fluxes in the plasma sheet. H+ is shown to be the dominant ion in the plasma sheet in the calm‐to‐storm transition. However, the energy‐flux of each ion changes in a quasi‐linear manner during extended calm intervals. Heavy ions (O+ and He+) become increasingly important during such periods as charge‐exchange reactions result in faster loss for H+ than for O+ or He+. Results confirm previous investigations showing that the ion composition of the plasma sheet can be largely understood (and predicted) during calm intervals from knowledge of (a) the composition of previously injected plasma at the onset of calm conditions and (b) use of simple drift‐physics models combined with calculations of charge‐exchange losses.
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