The role of electrons during chorus intensification: Energy source and energy loss

The role of electrons during the shock-induced chorus intensification observed by THEMIS D on 19 November 2007 is investigated in detail. First, the electrons are accelerated through the local betatron acceleration and radial diffusion, which are primarily in the perpendicular direction and result in the positive anisotropy (T-perpendicular to > T-//) of electrons; then they are scattered through the pitch-angle diffusion, during which the electron energies are partially transferred to amplify the chorus. In the case of interest, the energy loss is more efficient for the lower-energy (15 key) electrons because they have larger density gradient along the diffusion curves. The energetic electrons act as the intermediate in this scenario. They transfer the energies carried by the interplanetary shock to the chorus. The energetic electrons injected from magnetotail are not observed; they have no contributions to the energy source in this event. (C) 2012 Elsevier Ltd. All rights reserved.