Unified treatment of mean-field dynamo and angular-momentum transport in magnetorotational instability-driven turbulence
arXiv:2307.01281 · doi:10.1103/PhysRevE.108.065201
Abstract
Magnetorotational instability (MRI)-driven turbulence and dynamo phenomena are analyzed using direct statistical simulations. Our approach begins by developing a unified mean-field model that combines the traditionally decoupled problems of the large-scale dynamo and angular-momentum transport in accretion disks. The model consists of a hierarchical set of equations, capturing up to the second-order cumulants, while a statistical closure approximation is employed to model the three-point correlators. We highlight the web of interactions that connect different components of stress tensors -- Maxwell, Reynolds, and Faraday -- through shear, rotation, correlators associated with mean fields, and nonlinear terms. We determine the dominant interactions crucial for the development and sustenance of MRI turbulence. Our general mean field model for the MRI-driven system allows for a self-consistent construction of the electromotive force, inclusive of inhomogeneities and anisotropies. Within the realm of large-scale magnetic field dynamo, we identify two key mechanisms -- the rotation-shear-current effect and the rotation-shear-vorticity effect -- that are responsible for generating the radial and vertical magnetic fields, respectively. We provide the explicit (nonperturbative) form of the transport coefficients associated with each of these dynamo effects. Notably, both of these mechanisms rely on the intrinsic presence of large-scale vorticity dynamo within MRI turbulence.
32 pages including 25 figures; Version accepted for publication in Phys. Rev. E
References in corpus (19)
- First M87 Event Horizon Telescope Results. VIII. Magnetic Field Structure near The Event Horizon
- Direct simulations of a supernova-driven galactic dynamo
- Generation of Magnetic Field by Combined Action of Turbulence and Shear
- On Self-Sustained Dynamo Cycles in Accretion Discs
- Effects of fluctuation on alpha-omega dynamo models
- Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection
- Galactic Dynamos
- A Local Model for Angular Momentum Transport in Accretion Disks Driven by the Magnetorotational Instability
- The fundamental difference between shear alpha viscosity and turbulent magnetorotational stresses
- Do mean-field dynamos in nonrotating turbulent shear-flows exist?
- On self-sustaining processes in Rayleigh-stable rotating plane Couette flows and subcritical transition to turbulence in accretion disks
- Statistical simulation of the magnetorotational dynamo
- Subcritical dynamos in shear flows
- Magnetorotational instability with smoothed particle hydrodynamics
- Simulating the magnetorotational instability on a moving mesh with the shearing box approximation
- Magnetic helicity fluxes from triple correlators
- Compressible test-field method and its application to shear dynamos
- Turbulent stresses as a function of shear rate in a local disk model
- On the shear-current effect: toward understanding why theories and simulations have mutually and separately conflicted