Electrostatic solitary waves associated with plasma jet fronts in Earth's magnetotail

Plasma jets in the magnetotail are important carriers of energy and mass in the magnetospheric space. The energy and mass transport processes driven by them play a decisive role in the evolution of geomagnetic substorms and auroras. During their earthward propagation, the leading edges of these jets interact with the surrounding plasma, exciting various types of electromagnetic and electrostatic waves. This study aims to conduct a detailed statistical analysis of the physical characteristics of electrostatic solitary waves (ESWs) near the plasma jet fronts. Using high-resolution data from NASA's Magnetospheric Multiscale (MMS) mission, we calculated the propagation velocity, temporal scale, spatial scale, and electric potential of ESWs. The results show that: 1) The propagation speeds of ESWs span a wide range, from several hundred kilometers per second (close to the ion thermal speed) to tens of thousands of kilometers per second (close to the electron thermal speed), indicating that multiple generation mechanisms exist at the plasma jet fronts, including ion-electron beam (Buneman) instability and electron beam instability; 2) The period of ESWs is inversely proportional to their propagation speed, meaning that their spatial scales vary within a relatively narrow range, typically on the order of tens of Debye lengths; 3) The electric potential of ESWs is proportional to their spatial scale. Correlation analysis with local physical parameters reveals that these waves predominantly occur in regions of strong magnetic field behind the leading edge, i.e., within flux pileup regions. Moreover, the wave potential is positively correlated with the local electron temperature, suggesting that wave-electron interactions contribute to local electron heating. The findings of this study will help advance the understanding of wave-particle interactions in magnetospheric space.