Magnetic Reconnection Driven by the Impact of a Magnetosheath High‐Speed Jet

Abstract

Abstract High‐speed jets (HSJs) are transient structures in the magnetosheath characterized by enhanced dynamic pressure. While recent studies report that HSJs trigger magnetic reconnection at the magnetopause, whether they can directly drive reconnection within the magnetosheath remains an open question. Using Magnetospheric Multiscale (MMS) observations, we provide direct evidence of an HSJ driving magnetic reconnection within the magnetosheath. We show that as an earthward‐moving HSJ interacted with sunward ambient flows, it strongly compressed the local plasma, thereby forming an intense current sheet with a guide field. Within this current sheet, MMS detected clear reconnection signatures, including Hall electromagnetic fields, super‐Alfvénic electron jets, and electron demagnetization near the electron diffusion region. Evaluating diamagnetic drift criteria reveals that this compression overcame theoretical suppression conditions, facilitating the occurrence of reconnection. These results establish HSJs as key drivers of magnetic reconnection in the turbulent magnetosheath.