Direct Measurement of the Dissipation Rate Spectrum around Ion Kinetic Scales in Space Plasma Turbulence

The energy of turbulence in the universe, which cascades from large fluid scales to small kinetic scales, is believed to be dissipated through conversion to thermal or nonthermal kinetic energy. However, identifying the dissipation processes and measuring the dissipation rate in turbulence remain challenging. Based on unprecedented high-quality measurements of space plasma turbulence by the Magnetospheric Multiscale mission, we propose a novel approach to measure the scale-dependent spectrum of the energy conversion rate between the fluctuating electromagnetic energy and plasma kinetic energy. The energy conversion rate spectrum is found to show a positive bulge around the ion kinetic scale, which clearly indicates the dissipation of the turbulent energy. The energy dissipation rate around the ion scale is estimated to be 0.5 x 10(6) J kg(-1) s(-1). This work provides basic information on local dissipation in magnetosheath turbulence and sets up a new paradigm for studying the dissipation of universal plasma turbulence.