The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses

Abstract

Numerical simulations of turbulent, magnetized, differentially rotating flows driven by the magnetorotational instability are often used to calculate the effective values of alpha viscosity that is invoked in analytical models of accretion discs. In this paper we use various dynamical models of turbulent magnetohydrodynamic stresses, as well as numerical simulations of shearing boxes, to show that angular momentum transport in MRI-driven accretion discs cannot be described by the standard model for shear viscosity. In particular, we demonstrate that turbulent magnetorotational stresses are not linearly proportional to the local shear and vanish identically for angular velocity profiles that increase outwards.

Updated to match published version in MNRAS, 8 pages, 1 figure

References in corpus (22)

• The inverse cascade and nonlinear alpha-effect in simulations of isotropic helical hydromagnetic turbulence
• Enhanced Angular Momentum Transport in Accretion Disks
• On the Dynamical Foundations of Alpha Disks
• Global Magnetohydrodynamical Simulations of Accretion Tori
• Angular Momentum Transport by MHD Turbulence in Accretion Disks: Gas Pressure Dependence of the Saturation Level of the Magnetorotational Instability
• Hydrodynamic turbulence cannot transport angular momentum effectively in astrophysical disks
• Magnetohydrodynamical Non-radiative Accretion Flows in Two-Dimensions
• Global MHD Simulation of the Inner Accretion Disk in a Pseudo-Newtonian Potential
• Turbulence and angular momentum transport in a global accretion disk simulation
• Local Hydrodynamic Stability of Accretion Disks
• Angular Momentum Transport in Accretion Disks: Scaling Laws in MRI-driven Turbulence
• An Incoherent $\alpha -\Omega$ Dynamo in Accretion Disks
• Global MHD Simulations of Cylindrical Keplerian Disks
• The Stability of Magnetized Rotating Plasmas with Superthermal Fields
• Bypass to Turbulence in Hydrodynamic Accretion: Lagrangian Analysis of Energy Growth
• Geometrically Thin Disk Accreting Into a Black Hole
• On the dynamics of magnetorotational turbulent stresses
• Bypass to Turbulence in Hydrodynamic Accretion Disks: An Eigenvalue Approach
• The signature of the magnetorotational instability in the Reynolds and Maxwell stress tensors in accretion discs
• An Exact, Three-Dimensional, Time-Dependent Wave Solution in Local Keplerian Flow
• A Local Model for Angular Momentum Transport in Accretion Disks Driven by the Magnetorotational Instability
• Chaos in Turbulence Driven by the Magnetorotational Instability

Cited by in corpus (34)

• Are the Variations in Quasar Optical Flux Driven by Thermal Fluctuations?
• A Global Three Dimensional Radiation Magneto-hydrodynamic Simulation of Super-Eddington Accretion Disks
• Magnetic self-organisation in Hall-dominated magnetorotational turbulence
• Rotating Accretion Flows: From Infinity to the Black Hole
• Advection/Diffusion of Large-Scale B-Field in Accretion Disks
• On Self-Sustained Dynamo Cycles in Accretion Discs
• The Shakura-Sunyaev Viscosity Prescription with Variable alpha(r)
• End-to-end kilonova models of neutron-star mergers with delayed black-hole formation
• Jet Luminosity From Neutrino-Dominated Accretion Flows in Gamma-Ray Bursts
• Characterizing the mean-field dynamo in turbulent accretion disks
• Angular Momentum Transport in Protoplanetary and Black-Hole Accretion Disks: The Role of Parasitic Modes in the Saturation of MHD Turbulence
• Hydrodynamical numerical simulation of wind production from black hole hot accretion flows at very large radii
• MHD Simulation of a Disk Subjected to Lense-Thirring Precession
• Magneto-hydrodynamical Numerical simulation of wind production from black hole hot accretion flows at very large radii
• Evolution of the Solar Nebula. IX. Gradients in the Spatial Heterogeneity of the Short-Lived Radioisotopes ${}^{60}$Fe and ${}^{26}$Al and the Stable Oxygen Isotopes
• The Origin of Exponential Star-forming Disks
• Reynolds stresses from hydrodynamic turbulence with shear and rotation
• On the Time Variability of Geometrically-Thin Black Hole Accretion Disks II: Viscosity-Induced Global Oscillation Modes in Simulated Disks
• On Hydromagnetic Stresses in Accretion Disk Boundary Layers
• Accretion Disks and Dynamos: Toward a Unified Mean Field Theory
• MRI turbulence in accretion discs at large magnetic Prandtl numbers
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Comparisons and Connections between Mean Field Dynamo Theory and Accretion Disc Theory
• Interaction of the magnetorotational instability with hydrodynamic turbulence in accretion disks
• Sensitivity of the Magnetorotational Instability to the shear parameter in stratified simulations
• Oscillations of the Inner Regions of Viscous Accretion Disks
• A heuristic model for MRI turbulent stresses in Hall MHD
• Turbulence Closure for Mixing Length Theories
• MRI turbulence in vertically stratified accretion discs at large magnetic Prandtl numbers
• Identifying Deficiencies of Standard Accretion Disk Theory: Lessons from a Mean-Field Approach
• Neutrino oscillations in a neutrino-dominated accretion disk around a Kerr BH
• Unified treatment of mean-field dynamo and angular-momentum transport in magnetorotational instability-driven turbulence
• Turbulent viscosity by convection in accretion discs - a self-consistent approach
• An effective model for magnetic field amplification by the magnetorotational and parasitic instabilities