Energy Transfer and Electron Heating in Turbulent Flux Pileup Region

We report observations of intense energy transfer developed within a flux pileup region (FPR) inside a plasma jet in the Earth's midtail. Strong electromagnetic turbulences, with (Formula presented.) ((Formula presented.) and (Formula presented.) are wave numbers perpendicular and parallel to background magnetic field respectively), are observed together with intermittent sub-ion-scale structures, generating intense fluctuating electric fields and currents inside the FPR. The highly anisotropic turbulence is carried by kinetic Alfvénic waves with (Formula presented.) ((Formula presented.) is ion gyroradius), which are weakly damped due to electron Landau resonance and cause electron heating with a ratio close to 4 eV/s. Concurrent with the ion-scale turbulences and structures, strong energy conversion occurs inside the FPR (stronger than that at the jet front), with magnetic field energy being dissipated into particle energy, leading to efficient electron acceleration. These results highlight the crucial role played by turbulent FPRs in energy transfer in the magnetosphere.