The First Phase Diagram for the Dissipation of Astrophysical Plasma Turbulence*

A specific set of dimensionless plasma and turbulence parameters is introduced to characterize the nature of turbulence and its dissipation in weakly collisional space and astrophysical plasmas. To develop predictive models of the turbulent plasma heating that characterize the partitioning of dissipated turbulent energy between the ion and electron species and between the perpendicular and parallel degrees of freedom, it is essential to identify the kinetic physical mechanisms that govern the damping of the turbulent fluctuations. A set of ten general plasma and turbulence parameters are defined, and reasonable approximations, along with turbulence scaling theories, are used to reduce this general set to just three parameters in the isotropic temperature case: the ion plasma beta, the ion-to-electron temperature ratio, and the isotropic driving wavenumber. A critical step forward in this study is to identify the dependence of all of the proposed kinetic mechanisms for turbulent damping in terms of the same set of fundamental parameters. The scaling of each damping mechanism on these fundamental parameters is used to construct the first phase diagram for the turbulent damping mechanisms as a function of the ion plasma beta and isotropic driving wavenumber.