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Magnetorotational Turbulence and Dynamo in a Collisionless Plasma

Author(s): Kunz, Matthew W; Stone, James M; Quataert, E

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Abstract: © 2016 American Physical Society.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.
Publication Date: 1-Dec-2016
Citation: Kunz, MW, Stone, JM, Quataert, E. (2016). Magnetorotational Turbulence and Dynamo in a Collisionless Plasma. Physical Review Letters, 117 (23), 10.1103/PhysRevLett.117.235101
DOI: doi:10.1103/PhysRevLett.117.235101
ISSN: 0031-9007
EISSN: 1079-7114
Pages: 235101-1 to 235101-6
Type of Material: Journal Article
Journal/Proceeding Title: Physical Review Letters
Version: Final published version. Article is made available in OAR by the publisher's permission or policy.

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