Magnetorotational Turbulence and Dynamo in a Collisionless Plasma

Abstract

We present results from the first 3D kinetic numerical simulation of magnetorotational turbulence and dynamo, using the local shearing-box model of a collisionless accretion disc. The kinetic magnetorotational instability grows from a subthermal magnetic field having zero net flux over the computational domain to generate self-sustained turbulence and outward angular-momentum transport. Significant Maxwell and Reynolds stresses are accompanied by comparable viscous stresses produced by field-aligned ion pressure anisotropy, which is regulated primarily by the mirror and ion-cyclotron instabilities through particle trapping and pitch-angle scattering. The latter endow the plasma with an effective viscosity that is biased with respect to the magnetic-field direction and spatio-temporally variable. Energy spectra suggest an Alfvén-wave cascade at large scales and a kinetic-Alfvén-wave cascade at small scales, with strong small-scale density fluctuations and weak non-axisymmetric density waves. Ions undergo non-thermal particle acceleration, their distribution accurately described by a kappa distribution. These results have implications for the properties of low-collisionality accretion flows, such as that near the black hole at the Galactic center.

6 pages, 6 figures, accepted for publication in Physical Review Letters

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Cited by in corpus (14)

• The Radiative Efficiency and Spectra of Slowly Accreting Black Holes from Two-Temperature GRRMHD Simulations
• Fully kinetic versus reduced-kinetic modelling of collisionless plasma turbulence
• Suppression of electron thermal conduction by whistler turbulence in a sustained thermal gradient
• How important is non-ideal physics in simulations of sub-Eddington accretion onto spinning black holes?
• Pair Drizzle around Sub-Eddington Supermassive Black Holes
• Shearing-box simulations of MRI-driven turbulence in weakly collisional accretion discs
• Dynamo Action in a Quasi-Keplerian Taylor-Couette Flow
• Particle Diffusion and Acceleration in Magnetorotational Instability Turbulence
• Accretion of a Vlasov gas on to a black hole from a sphere of finite radius and the role of angular momentum
• Braginskii viscosity on an unstructured, moving mesh accelerated with super-time-stepping
• Weakly magnetized, Hall dominated plasma Couette flow
• Universal small-scale structure in turbulence driven by magnetorotational instability
• Time Domain Filtering of Resolved Images of Sgr A*
• Discrete Symmetries in Dynamo Reversals