2016/08/31 by Matthew W. Kunz, James M. Stone, Eliot Quataert · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Classical mechanics #Computational physics #Dynamo #Gyroradius #Instability #Magnetic field #Magnetohydrodynamics #Magnetorotational instability #Mechanics #Physics #Solar and Space Plasma Dynamics #Turbulence #astro-ph.HE #physics.plasm-ph
paper · pdf · doi:10.1103/physrevlett.117.235101
published as Phys. Rev. Lett. 117, 235101 (2016) · 6 pages, 6 figures, accepted for publication in Physical Review Letters
arxiv created 2016/10/19 · openalex publication_date 2016/12/01 · arxiv updated 2016/12/07 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
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 disk. 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 spatiotemporally 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 nonaxisymmetric density waves. Ions undergo nonthermal particle acceleration, their distribution accurately described by a κ distribution. These results have implications for the properties of low-collisionality accretion flows, such as that near the black hole at the Galactic center.