2005/08/25 by Prateek Sharma, Gregory W. Hammett, G. W. Hammett +2
Physics and Astronomy · #Angular momentum #Anisotropy #Astrophysical Phenomena and Observations #Astrophysics and Star Formation Studies #Classical mechanics #Computational physics #Gamma-ray bursts and supernovae #Instability #Magnetic field #Magnetohydrodynamics #Magnetorotational instability #Mechanics #Optics #Physics #Plasma #Quantum mechanics #Reynolds stress #Shearing (physics) #Turbulence #astro-ph #physics.plasm-ph #physics.space-ph
paper · pdf · doi:10.1086/498405
published as Astrophys.J.637:952-967,2006 · 20 pages, 9 figures, submitted to ApJ
arxiv created 2005/08/25 · openalex publication_date 2006/01/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We describe local shearing box simulations of turbulence driven by the magnetorotational instability (MRI) in a collisionless plasma. Collisionless effects may be important in radiatively inefficient accretion flows, such as near the black hole in the Galactic center. The MHD version of ZEUS is modified to evolve an anisotropic pressure tensor. A fluid closure approximation is used to calculate heat conduction along magnetic field lines. The anisotropic pressure tensor provides a qualitatively new mechanism for transporting angular momentum in accretion flows (in addition to the Maxwell and Reynolds stresses). We estimate limits on the pressure anisotropy due to pitch angle scattering by kinetic instabilities. Such instabilities provide an effective "collision" rate in a collisionless plasma and lead to more MHD-like dynamics. We find that the MRI leads to efficient growth of the magnetic field in a collisionless plasma, with saturation amplitudes comparable to those in MHD. In the saturated state, the anisotropic stress is comparable to the Maxwell stress, implying that the rate of angular momentum transport may be moderately enhanced in a collisionless plasma.