Geospace driver effects on electron acceleration and loss in the outer Van Allen belt

Abstract:

Understanding the role of interplanetary and geospace drivers in the emergence of relativistic and ultra-relativistic electrons is of utmost importance for the best possible specification and prediction of their fluxes in the outer Van Allen belt. In this work we investigate the response of the outer Van Allen belt electron phase space density (PSD) in invariant coordinates to various types of solar wind and internal magnetospheric forcing. We have employed multi-point particle and field observations in the inner magnetosphere (both in-situ and through ground-based remote sensing), providing a broad range of particle energies and a wide radial and azimuthal spatial coverage using a database of more than 70 events from 2013 to 2016.

From our statistical results, the evolution in the time profile of electron PSD show that over 60% of the events resulted in PSD increase (dominated by ICME driven storms), ~20% resulted in PSD decrease (dominated by HSS driven and weak storms) while the rest had μ- and K-dependent results. We also show that – for similar duration and power – acceleration by chorus waves exceeds outward diffusion driven by Pc5 activity. In ~85% of events, Poloidal and Toroidal mode waves are well correlated with the AL index and thus the substorm activity. On the other hand, Compressional mode waves are well correlated with Sym-H index and solar wind pressure.