On radiation belt dynamics during magnetic storms

Abstract

Temporal variations of the radiation belt particle during the magnetic storms are investigated using measurements by the low altitude satellite spectrometer. Along with several known effects, such as the outer radiation belt intensity decrease at the main phase, the radial diffusion with the particle acceleration and the recovery of the radiation belt during the recovery phase, some less known features were investigated, such as the dawn–dusk asymmetry of the radiation belt. During the main phase in the dusk sector an extension of the outer magnetic field lines into magnetotail occurs, the electron flux previously measured in the outer radiation belt maximum decreases to the polar cap level. All three adiabatic invariants remain conserved during this transformation and as a consequence the radiation belt became adiabatically shifted to the lower latitudes with addition of the nonadiabatic radial displacement. During the main phase in the dawn sector the chain of the substorm dipolarizations is acting against the tailward magnetic field line extension produced by the ring current and satellite registers an enhanced particle flux in the quasitrapping region. The adiabatic recovery of the radiation belt take place at the end of the magnetic storm again with the addition of the nonadiabatic effects caused by the substorm activity. It seems that a essential part of the radiation belt temporal dynamics during magnetic storms may be explained by the change of the magnetic field configuration and the adiabatic effects. Together with the nonadiabatic radial diffusion it results in the radial displacement of the outer radiation belt rather than the large losses or total disappearance of the outer radiation belt.