On the use of kinetic entropy to identify kinetic-scale energy transfer and dissipation

The transfer and dissipation of energy at small scales in weakly collisional systems are crucial to many important plasma processes, such as magnetic reconnection, plasma turbulence, and collisionless shocks. The plasmas in which these processes occur are often far from local thermodynamic equilibrium, where kinetic physics plays an important role in the dynamics. A number of measures have been developed to identify locations where small scale energy transfer and dissipation takes place in numerical simulations and in satellite observations. We investigate the use of kinetic entropy, the entropy within the kinetic theory description of a plasma, to identify and facilitate the study of such processes. We study a kinetic entropy-based measure of non-Maxwellianity in the context of magnetic reconnection from three viewpoints: theoretically, numerically using particle-in-cell simulations of magnetic reconnection, and observationally using the Magnetospheric Multiscale (MMS) satellites.