Quasi‐Trapped Electron Fluxes Induced by NWC Transmitter and CRAND: Observations and Simulations

Abstract

AbstractSignals from the NWC ground‐based very low frequency (VLF) transmitter can leak into the magnetosphere and scatter trapped energetic electrons into drift loss cones. Recent studies also suggest that cosmic ray albedo neutron decay (CRAND) is probably an important source for quasi‐trapped electrons in the inner belt. To investigate their relative contributions, this study comprehensively analyzes the long‐term variations of quasi‐trapped 206 keV electrons at L = 1.7, which is roughly the L shell where NWC is located. Furthermore, a drift‐diffusion‐source model is used to reproduce longitudinal distributions of quasi‐trapped electrons and investigate sensitivities of simulation results to VLF transmitter intensities. These results suggest that CRAND is the main source of quasi‐trapped hundreds of keV electrons when the NWC station is at dayside. In contrast, pitch angle diffusions become the main source mechanism of these quasi‐trapped electrons when the NWC station operates at nightside with more VLF transmitter energy leaking into the magnetosphere.