Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows

Shigeo S. Kimura, Kengo Tomida, Kohta Murase

Research output: Contribution to journalArticle

6 Citations (Scopus)

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: Dϵ ϵ2, where ϵ 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 ϵ ∼0.1-10 PeV.

Original languageEnglish (US)
Pages (from-to)163-178
Number of pages16
JournalMonthly Notices of the Royal Astronomical Society
Volume485
Issue number1
DOIs
StatePublished - May 1 2019

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particle energy
escape
turbulence
accretion
energy
magnetic field configurations
magnetohydrodynamic simulation
relativistic particles
particle acceleration
active galactic nuclei
diffusion coefficient
actuators
particle
vortices
orbits
magnetohydrodynamics
propagation
probes
eddy
configurations

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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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: Dϵ ϵ2, where ϵ 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 ϵ ∼0.1-10 PeV.",
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Acceleration and escape processes of high-energy particles in turbulence inside hot accretion flows. / Kimura, Shigeo S.; Tomida, Kengo; Murase, Kohta.

In: Monthly Notices of the Royal Astronomical Society, Vol. 485, No. 1, 01.05.2019, p. 163-178.

Research output: Contribution to journalArticle

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