Global Thermodynamics and Particle Heating in Radiatively Inefficient Accretion Flows

In the collisionless plasmas of radiatively inefficient accretion flows, the heating and acceleration of ions and electrons is not well understood. Recent studies in the gyrokinetic limit revealed the importance of incorporating both the compressive and Alfvenic cascades when calculating the partition of dissipated energy between the plasma species resulting from collisionless damping. In this talk, I will discuss the impact of particle heating in the presence of compressive and Alfven waves, Coulomb collisions, compressional heating, and radiative cooling on the radial temperature profiles of ions and electrons as well as establish the importance of the relative driving power of compressive and Alfvenic turbulence in determining the ion-to-electron temperature ratio. I will then provide a physically motivated expression for this temperature ratio in the inner accretion flow around a black hole, that can be used to calculate observables from general relativistic magneto-hydrodynamic (MHD) simulations. The relative power in the compressive and Alfvenic cascades is determined at the driving scales of the accretion disk turbulence, primarily by the dynamics of the magneto-rotational instability. I will establish the physical mechanism of the turbulent power injected into the compressive and Alfvenic cascades in turbulence driven by the magneto-rotational instability and connect them to the Maxwell and Reynolds stress tensors. I will present numerical computations of the relative driving power between the cascades using local shearing-box MHD simulations and discuss its importance in the context of GRMHD simulations.