Origin of ultrastrong energy transfer at magnetic reconnection fronts

Magnetic reconnection, a fundamental process in laboratory, space and astrophysical plasmas, can transfer magnetic field energy into particles’ kinetic and thermal energy, leading to many explosive phenomena, such as solar flares and astrophysical jets. It has been believed that reconnection-driven energy transfer typically occurs inside reconnection ejecta, particular reconnection fronts (RFs), which can host localized, ultrastrong energy transfer (UET) directly controlling large-scale energy transport. However, origin of the RF-driven UET remains unclear. Here, using state-of-the-art measurements from NASA’s Magnetospheric Multiscale (MMS) spacecraft, we perform a comprehensive investigation of UET at RFs. We reveal that the UET hosts two different regimes: ion-dominated laminar regime and electron-dominated turbulent regime. The transition between the two regimes is controlled by an electron-ion hybrid instability, which can generate lower hybrid turbulence feeding intense electric fields. We find that Hall term in the generalized Ohm’s law, rather than traditionally-believed electron pressure gradient term, plays a more significant role in balancing the intense electric fields. These results provide novel insights into understanding reconnection-driven energy transport chain widely present in the cosmos.