Energy Conversion and Partition in Plasma Turbulence Driven by Magnetotail Reconnection

A long-outstanding issue in fundamental plasma physics is how magnetic energy is finally dissipated in kinetic scale in the turbulent plasma. Based on the Magnetospheric Multiscale mission data in the plasma turbulence driven by magnetotail reconnection, we establish the quantitative relation between energy conversion (J·E , J is current density and E is electric field) and current density (J). The results show that the magnetic energy is primarily released in the perpendicular directions (up to 90%), in the region with current density less than 2.3 J_rms, where J_rms  is the root mean square value of the total current density J. In the relatively weak current region (< 1.0 J_rms ), the ions get most of the released energy while the largely negative energy conversion rate of the electrons means a dynamo action. In the strong currents (>1.0 J_rms), the ion energization was negligible and the electrons are significantly energized. Moreover, a linearly increasing relationship was established between J·E and J. The observations indicate that ions overall dominate energy conversion in turbulence, but the electron dynamics are crucial for energy conversion in intense currents and the turbulence evolution.