Manifestation of the ion-acoustic instability in magnetic reconnection

We report first-principles numerical investigations of magnetic reconnection focusing on regimes characterized by low ion-to-electron temperature ratios, relevant to space and astrophysical plasmas and to the solar wind. We provide robust numerical evidence for the existence of the ion-acoustic instability driven by in-plane electron-ion drift velocities in excess of the ion sound speed within the diffusion region of a reconnecting magnetic configuration. Our analysis reveals that this instability induces significant ion heating near the x-line and at the separatrix, primarily through ion-acoustic waves identified in simulations, highlighting their crucial role in energy transfer during magnetic reconnection. The implications of these findings on reconnection dynamics are discussed, shedding new light on the fundamental processes present in collisionless reconnection.

The authors thank K. G. Miller for insight on PIC simulations and M. Zhou for stimulating discussions.