Excitation characterization of whistler waves and electrostatic oscillation in asymmetric magnetic reconnection

Utilizing the 2.5D Particle-in-Cell (PIC) method, we observe that large-amplitude whistler waves are present near the separatrix on the magnetospheric side and in the outflow region during asymmetric magnetic reconnection. Minimum variance analyses confirm their quasi-parallel and anti-parallel propagation to the background magnetic field, respectively, and their accuracy is validated through parallel Poynting fluxes (S∥). The excited whistler waves have intermittent property due to the evolution and movement of the reconnection layer. Wave-Particle Interaction Analysis (WPIA) reveals a pronounced energy conversion between the waves and electrons. Our simulation results demonstrate that whistler waves near the separatrix are excited by the cyclotron resonance duo to the instability of electron beam by analyzing the electron velocity distribution functions (VDFs). Meanwhile, the electrostatic oscillation is generated by the positive parallel drift of electron beam. However, the whistler waves in the outflow region are excited by the Landau resonance duo to anisotropic instability distributions of electron beam-mode.