Speaker
Description
Hot accretion flows contain collisionless plasmas under turbulence generated by the magnetorotational instability (MRI), which can be potential source of particle acceleration. We conduct unstratified shearing-box magnetohydrodynamic (MHD) simulations of the MRI turbulence with net vertical magnetic flux, with and without explicit dissipation, and inject relativistic test particles in simulation snapshots. The results are analyzed by applying the Fokker-Planck equation to particle momentum evolution. We find that the particle momentum diffusion coefficient scales as 𝐷(𝑝) ∝ 𝑝, for lower-energy particles, and shear acceleration takes over when particle gyro-radius 𝑅𝑔 ≳ 0.1𝐻. There also appear to be an anomalous direct acceleration/deceleration, likely associated with the intermittency in the MRI turbulence, and is affected by the turbulence Prandtl number. We also discuss the potential of accelerating PeV cosmic-rays in hot accretion flows around supermassive black holes.
