Dynamics of energetic ions and electrons between L = 2.5 and L = 7 during magnetic storms

Abstract

The variation of energetic electron and ion fluxes with L values between 2.5 and 7 as measured by two magnetic spectrometers (medium electrons A and B, MEA and MEB) on CRRES will be presented for one intense and two weak magnetic storms, paying particular attention to the rate of accompanying substorms. Electrons in the energy range 45–602 keV and ions in the range 77–703 keV will be examined. The data are presented in cuts through L versus time plots which are ideal to demonstrate the global aspect and the long‐term variations of a magnetic storm in the outer radiation belt. The time resolution is half an orbital period of CRRES (5.5 hours). Substantial decreases and enhancements of electron and ion intensity are seen at the beginning and recovery of intense magnetic storms (Dst < −100 nT). Electrons and ions are shifted to lower L values during these storms and the slot region narrows for ions. The slot region can disappear completely for electrons during the recovery of the storm. For small magnetic storms (Dst about −30 nT), which seem to be caused by a series of substorms, the ring current does not move to lower L values and stays at L values of about 5.5 but weakens, even though Dst decreases. This is attributed to the strong substorm current systems. Knowledge of the past history of the radiation belts is required to separate “true” storm time depressions of Dst from substorm‐related effects.