Particle diffusion and acceleration in magnetorotational instability turbulence

Hot accretion flows contain collisionless plasmas that are believed to be capable of accelerating particles very high energies, as a result turbulence generated by the magnetorotational instability (MRI). We conduct unstratified shearing-box simulations MRI in ideal magnetohydrodynamic (MHD), and inject energetic (relativistic) test simulation snapshots detailed investigation on particle diffusion stochastic acceleration. consider different amount net vertical magnetic flux achieve disk magnetizations levels at saturated states, with sufficiently resolution resolve gyro-radii ($R_g$) most particles. Particles large $R_g$ ($\gtrsim0.03$ scale height $H$) show spatial coefficients $\sim30$ $\sim5$ times Bohm values azimuthal poloidal directions, respectively. further measure momentum coefficient $D(p)$ applying Fokker-Planck equation evolution. For these particles, contribution from turbulent fluctuations scales $D(p)\propto p$, shear acceleration takes over when $R_g\gtrsim0.1H$, characterized p^3$. smaller ($\lesssim0.03H$), their roughly $\sim p^{-1}$, evidence p^2$ scaling but uncertainties. find multiple effects contribute acceleration/deceleration, process is also likely affected intermittency turbulence. discuss potential PeV cosmic-rays hot around supermassive black holes.