Dissipation measures in weakly collisional plasmas

The physical foundations of energy dissipation and heating in weakly collisional plasmas are poorly understood. Here, we compare several measures largely used to characterize energy dissipation and kinetic-scale conversion in plasmas by means of a suite of kinetic numerical simulations describing both magnetic reconnection and decaying plasma turbulence. We differentiate between i) energy-based parameters, whose definition is related to energy transfer in a fluid description of the plasma, and ii) distribution function-based parameters, requiring knowledge of the particle velocity distribution function. Dissipation occurs close to regions of intense magnetic stresses. The distribution function-based measures show a broader width compared to energy-based proxies, suggesting that energy transfer is co-localized at coherent structures, but can affect the particle distribution function in wider regions. The effect of inter-particle collisions on these parameters is finally discussed.