The radiation belts are charged particles, trapped in the magnetic field of the Earth. The electron radiation belts consist of an inner belt and an outer belt. In the outer belt, electron flux variations of several orders of magnitude are correlated with geomagnetic storms. Geomagnetic storms are observed by variations in the Dst index, which is based on magnetic field measurements on the surface of the Earth. The main phase of a geomagnetic storm is observed by a rapid decrease of the Dst index. The recovery phase of a geomagnetic storm is a slow recovery of the magnetic field. Observations of the outer belt, show a spectacular electron dropout during the main phase.
To identify the transport, source, loss, acceleration, and deceleration effects of the physical processes of the radiation belts, we performed relativistic 3D test particle simulations. We launched electrons and protons at inner and outer belt locations, with keV to MeV energies, with different pitch angles, and magnetic local times. Modeling a magnetic field and induced electric field, the particles are decelerated and accelerated. Simulations show that during the main phase a particle loses 32 percent of its kinetic energy, while drifting radially outwards by one Earth radius. This is a first explanation for the observed dropout. The second explanation is that the particle will be transported outwards until magnetopause shadowing removes the particle from the outer radiation belt.