Impact of Interplanetary Coronal Mass Ejections on the dynamic variations of the electron population in the outer Van Allen belt

The outer Van Allen radiation belt is an environment with intense variability due to complex mechanisms that are part of the solar–terrestrial coupling. A fundamentally important effect is the acceleration of seed electrons to relativistic and ultra-relativistic energies. In our work, we examine 19 events from the Van Allen Probes era (2012 – 2018), which have been chosen according to the interplanetary driver of the geomagnetic disturbance. The selected events were driven by Interplanetary Coronal Mass Ejections (ICMEs). We have calculated the electron Phase Space Density (PSD) for distinct values of the first adiabatic invariant (μ = 100, 1000, 5000 MeV/G) corresponding to the different energies of the electrons in the outer radiation belt. Furthermore, we have studied the response of the electron population for different K values (second adiabatic invariant), in order to compare the differences between the two main acceleration mechanisms and their dependence on the electron pitch angle. This is achieved by performing a Superposed Epoch Analysis (SEA) of the geomagnetic disturbance events, taking into consideration the parameters of solar wind and the state of the magnetosphere. We compare and discuss the variability of the electron PSD for different values of the adiabatic invariants, the effects of the ICMEs on the outer radiation belt and how the different electron populations are affected.