# Acceleration and Escape Processes of High-energy Particles in Turbulence inside Hot Accretion Flows

## TL;DR

This study uses magnetohydrodynamic simulations to explore how turbulence in hot accretion flows accelerates high-energy particles, revealing diffusion in energy space and superdiffusion in space, with implications for cosmic ray acceleration in active galactic nuclei.

## Contribution

It provides a detailed analysis of particle acceleration mechanisms in hot accretion flows using simulations, highlighting the roles of turbulence and magnetic field configurations.

## Key findings

- Particle energy diffusion follows a $D_     $
- Superdiffusive behavior in configuration space indicates faster-than-normal radial displacement of particles.
- High-energy particles can be accelerated up to 0.1-10 PeV in active galactic nuclei with hot accretion flows.

## Abstract

We investigate acceleration and propagation processes of high-energy particles inside hot accretion flows. The magnetorotational instability (MRI) creates turbulence inside accretion flows, which triggers magnetic reconnection and may produce non-thermal particles. They can be further accelerated stochastically by the turbulence. To probe the properties of such relativistic particles, we perform magnetohydrodynamic simulations to obtain the turbulent fields generated by the MRI, and calculate orbits of the high-energy particles using snapshot data of the MRI turbulence. We find that the particle acceleration is described by a diffusion phenomenon in energy space with a diffusion coefficient of the hard-sphere type: $D_\epsilon\propto \epsilon^2$, where $\epsilon$ is the particle energy. Eddies in the largest scale of the turbulence play a dominant role in the acceleration process. On the other hand, the stochastic behaviour in configuration space is not usual diffusion but superdiffusion: the radial displacement increases with time faster than that in the normal diffusion. Also, the magnetic field configuration in the hot accretion flow creates outward bulk motion of high-energy particles. This bulk motion is more effective than the diffusive motion for higher energy particles. Our results imply that typical active galactic nuclei that host hot accretion flows can accelerate CRs up to $\epsilon\sim 0.1-10$ PeV.