Academic Journal

Energy Transfer and Electron Heating in Turbulent Flux Pileup Region.

Bibliographic Details
Title: Energy Transfer and Electron Heating in Turbulent Flux Pileup Region.
Authors: Liu, C. M., Cao, J. B., Wang, T. Y., Xing, X. N.
Source: Geophysical Research Letters; 12/28/2022, Vol. 49 Issue 24, p1-12, 12p
Subject Terms: PLASMA turbulence, TURBULENT heat transfer, ENERGY transfer, EDDY flux, ELECTRIC currents, HEAT flux
Company/Entity: UNITED States. National Aeronautics & Space Administration
Abstract: 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 k⊥≫k∥ ${k}_{\perp }\gg {k}_{{\Vert} }$ (k⊥ ${k}_{\perp }$ and k∥ ${k}_{{\Vert} }$ 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 k⊥ρi∼2 ${k}_{\perp }{\rho }_{i}\sim 2$ (ρi ${\rho }_{i}$ 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. Plain Language Summary: Plasma jets, traditionally termed as bursty bulk flows (BBFs) in the magnetotail, are responsible for energy transfer and transport in geospace. The jet‐driven energy transfer has been suggested to happen primarily at jet leading boundaries—dipolarization fronts (DFs) which are characterized by sharp enhancement of northward component of magnetic field at ion scale. Energy transfer behind the DFs has attracted few interests, because no intense currents and electric fields are typically anticipated inside flux pileup region (FPR) where magnetic field are typically strong and homogenous. In this study, different from such traditional perspective, we report observations of intense energy transfer developed within a turbulent FPR, using high‐cadence measurements from NASA's MMS mission. We show that ion‐scale turbulence and structures can develop inside the FPR, leading to efficient electron heating and acceleration therein. These results help better understand energy transport chain driven by BBFs in geospace. Key Points: Kinetic Alfvénic wave turbulence and intermittent structures are observed inside flux pileup region (FPR) within a plasma jetIntense energy transfer occurs inside the FPR, with magnetic field energy being dissipated into particle energyElectrons experience efficient acceleration and heating driven by various processes developed within the turbulent decaying FPR [ABSTRACT FROM AUTHOR]
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