Local wave acceleration or radial diffusion for radiation-belt electrons?
In plain words
Electrons in the outer radiation belt can be boosted to millions of electron volts, either by plasma waves right where they are or by being slowly pushed inward from farther out. The share of each process in a given storm is not known well enough to forecast.
Precise statement
For outer-belt electrons ($L \sim 3 \text{ to } 6$, energies 0.5 to 10 MeV), quantify during storms the relative contributions of local acceleration by whistler-mode chorus waves and inward radial diffusion driven by ULF waves, as functions of geomagnetic activity and seed population. An answer is an event-resolved partition validated by phase-space-density profiles at fixed adiabatic invariants.
What would settle it
Multi-spacecraft phase-space-density profiles at fixed invariants combined with data-driven Fokker-Planck models using measured wave power, reproducing flux enhancements across a statistical set of storms.
Status in the literature
Van Allen Probes data (2012 to 2019) showed growing local phase-space-density peaks in many storms, establishing local acceleration as important, but the event-by-event partition remains unpredicted.