Effective Viscosity, Resistivity and Reynolds Number in Weakly Collisional Plasma Turbulence

Energy dissipation is an energy conversion process, but specifically emphasizes the transformation of energy into heat. Energy dissipation mechanism for weakly collisional or collisionless plasma is of principal importance for addressing long-standing puzzles like the acceleration of energetic particles and the heating of the solar corona and solar wind. When collisions are strong in a magnetized plasma, standard closures provide simple representations of dissipation in terms of coefficients of viscosity and resistivity. In the opposite limit of weak collisions, the analogous physical effects that lead to dissipation are present, but the simple approximations to describe them, the closures, are not available in general. Fortunately, there is growing evidence suggesting possible similarities of collisionless dissipation to well-studied collisional dissipation. We employ kinetic Particle-in-Cell simulations of proton-electron plasma as well as in-situ observations from the Magnetospheric Multiscale mission, to examine analogous viscous-like and resistive-like scaling in the weakly collisional regime. This intriguing finding allows not only extraction of collisional-like viscosity and resistivity, but also direct determination of effective Reynolds number (in the form of viscosity and resistivity). The effective Reynolds number, as a measure of the available bandwidth for turbulence to populate various scale, links macro turbulence properties with kinetic plasma properties in a novel way.