Nongyrotropic Electron Distribution Functions and the Origin of Waves during Asymmetric Guide Field Reconnection

Abstract:

Magnetic reconnection is arguably the most important transport and energy conversion process in collisionless plasma. Electron distribution functions are good indicators to identify various locations in magnetic reconnection. In 2-D particle-in-cell (PIC) simulations of asymmetric guide field reconnection, highly structured electron distributions have been observed in the electron diffusion region (EDR) and exhaust regions including separatrices. The perpendicular/parallel crescent electron distribution functions have been observed in the EDR by MMS measurements. In 2-D PIC simulations, we observed enhancement of wave powers between the electron cyclotron frequency and the lower hybrid frequency during reconnection. At the same time, ring and perpendicular/parallel crescent electron distribution functions are generated in the EDR. We study interactions between electron beams and waves whose frequencies are in the range of whistler waves inside and outside of the EDR including separatrices, using fast Fourier transform of waves and analyses of electron distribution functions. We also investigate how these highly structured electron distribution functions are produced during asymmetric guide field reconnection, and the origin of the waves we observed in the reconnection.