EARTH
In the literature: open
What empties the outer radiation belt during sudden electron dropouts?
In plain words
Sometimes most of the high-energy electrons in the outer belt vanish within hours. They can be lost into the atmosphere or out through the edge of the magnetic field, and which route dominates is unclear.
Precise statement
For flux dropouts of relativistic electrons, quantify the fractions lost to the atmosphere by pitch-angle scattering from EMIC (electromagnetic ion cyclotron) waves, chorus and hiss, versus lost through the magnetopause by shadowing and outward radial transport. An answer is a loss budget per event constrained by simultaneous precipitation and in-situ flux measurements.
What would settle it
Conjugate low-orbit precipitation and equatorial in-situ measurements closing the electron loss budget for a set of dropout events.