Particle-In-Cell Simulations of Electrostatic Solitary Waves in Asymmetric Magnetic Reconnection

Electrostatic solitary waves (ESWs) are ubiquitously observed in magnetic reconnection. In this study, two-dimensional (2-D) particle-in-cell (PIC) simulations are performed to investigate the characteristics of ESWs in asymmetric magnetic reconnection. ESWs with bipolar structures of the parallel electric field can be generated near the separatrices only on the magnetosphere side, and propagate to reconnection downstream direction along the magnetic field. These structures corresponding to electron phase-space holes (electron holes) can cross both the electron outflow and inflow channels although their main part is located in the electron outflow. When there is no guide field, the ESWs are generated by electron two-stream instability. When there is a guide field, the amplitude of the ESWs are different on the right and left side of the X line. On the left side, the ESWs are weaker and generated by the electron two-stream instability. On the right side, the ESWs are stronger, and there are two kinds of ESWs with distinct phase speed. The faster one is generated by electron two-stream instability, while the slower one is generated by Buneman instability.