Magnetorotational instability driven dynamos at low magnetic Prandtl numbers

Abstract

Numerical simulations of the magnetorotational instability (MRI) with zero initial net flux in a non-stratified isothermal cubic domain are used to demonstrate the importance of magnetic boundary conditions.In fully periodic systems the level of turbulence generated by the MRI strongly decreases as the magnetic Prandtl number (Pm), which is the ratio of kinematic viscosity and magnetic diffusion, is decreased. No MRI or dynamo action below Pm=1 is found, agreeing with earlier investigations. Using vertical field conditions, which allow the generation of a net toroidal flux and magnetic helicity fluxes out of the system, the MRI is found to be excited in the range 0.1 < Pm < 10, and that the saturation level is independent of Pm. In the vertical field runs strong mean-field dynamo develops and helps to sustain the MRI.

8 pages, 7 figures, published version. Version with higher resolution figures is available at http://www.helsinki.fi/~kapyla/publ.html

References in corpus (31)

• Astrophysical magnetic fields and nonlinear dynamo theory
• The inverse cascade and nonlinear alpha-effect in simulations of isotropic helical hydromagnetic turbulence
• Sustained Magnetorotational Turbulence in Local Simulations of Stratified Disks with Zero Net Magnetic Flux
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. II. The effect of transport coefficients
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. I. The issue of convergence
• Hydromagnetic turbulence in computer simulations
• Magnetic Helicity Conservation and Astrophysical Dynamos
• Dynamic nonlinearity in large scale dynamos with shear
• Magnetic diffusivity tensor and dynamo effects in rotating and shearing turbulence
• Electromotive Force and Large-Scale Magnetic Dynamo in a Turbulent Flow with a Mean Shear
• Fluctuation dynamo and turbulent induction at low magnetic Prandtl numbers
• An Incoherent $\alpha -\Omega$ Dynamo in Accretion Disks
• Nonlinear theory of a "shear-current" effect and mean-field magnetic dynamos
• Large-scale dynamos in turbulent convection with shear
• The Nuclear Stellar Disk in Andromeda: A Fossil from the Era of Black Hole Growth
• Generation of Magnetic Field by Combined Action of Turbulence and Shear
• On Self-Sustained Dynamo Cycles in Accretion Discs
• Equatorial magnetic helicity flux in simulations with different gauges
• Magnetic helicity in stellar dynamos: new numerical experiments
• Effects of fluctuation on alpha-omega dynamo models
• Large-scale dynamos at low magnetic Prandtl numbers
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux: the case Pm=4
• The Saturation Limit of the Magnetorotational Instability
• The alpha effect in rotating convection with sinusoidal shear
• Geodynamo alpha-effect derived from box simulations of rotating magnetoconvection
• Magnetic helicity flux in the presence of shear
• Open and closed boundaries in large-scale convective dynamos
• Reynolds stresses from hydrodynamic turbulence with shear and rotation
• Comparisons and Connections between Mean Field Dynamo Theory and Accretion Disc Theory
• Turbulent stresses as a function of shear rate in a local disk model
• Influence of Ohmic diffusion on the excitation and dynamics of MRI

Cited by in corpus (39)

• Dynamo theories
• Astrophysical turbulence modeling
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Experimental evidence for non-axisymmetric magnetorotational instability in a rotating liquid metal exposed to an azimuthal magnetic field
• Global bifurcations to subcritical magnetorotational dynamo action in Keplerian shear flow
• Magnetic Prandtl number dependence of kinetic to magnetic dissipation ratio
• Local instabilities in magnetized rotational flows: A short-wavelength approach
• Stability and instability of hydromagnetic Taylor-Couette flows
• Magnetorotational turbulence transports angular momentum in stratified disks with low magnetic Prandtl number but magnetic Reynolds number above a critical value
• Magnetic Helicity and Large Scale Magnetic Fields: A Primer
• Statistical simulation of the magnetorotational dynamo
• Magnetorotational instability and dynamo action in gravitoturbulent astrophysical discs
• Extending the range of the inductionless magnetorotational instability
• The influence of accretion disk thickness on the large-scale magnetic dynamo
• Gravitoturbulent dynamos in astrophysical discs
• Global simulations of magnetorotational turbulence I: convergence and the quasi-steady state
• Dissipative effects on the sustainment of a magnetorotational dynamo in Keplerian shear flow
• Nonmodal growth of the magnetorotational instability
• Magnetorotational instability: nonmodal growth and the relationship of global modes to the shearing box
• Magnetorotational turbulence in stratified shearing boxes with perfect gas equation of state and finite thermal diffusivity
• Large scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability
• A unifying picture of helical and azimuthal MRI, and the universal significance of the Liu limit
• Saturation of the magnetorotational instability and the origin of magnetically elevated accretion discs
• Anomalous Low States and Long Term Variability in the Black Hole Binary LMC X-3
• Zero net flux MRI-turbulence in disks $-$ sustenance scheme and magnetic Prandtl number dependence
• Accretion Disks and Dynamos: Toward a Unified Mean Field Theory
• Simulations of a Magnetic Fluctuation Driven Large Scale Dynamo and Comparison with a Two-scale Model
• Magnetorotational instability with smoothed particle hydrodynamics
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Modelling supernova driven turbulence
• Turbulent transport in hydromagnetic flows
• Dynamo effects in magnetorotational turbulence with finite thermal diffusivity
• Global simulations of magnetorotational turbulence II: turbulent energetics
• A heuristic model for MRI turbulent stresses in Hall MHD
• Post-dynamical inspiral phase of common envelope evolution. The role of magnetic fields
• Gravito-turbulence and dynamo in poorly ionised protostellar discs. I. Zero-net-flux case
• Ribbons characterize magnetohydrodynamic magnetic fields better than lines: a lesson from dynamo theory
• Self-similar structure of resistive ADAFs with outflow and large-scale magnetic field
• Impact of magnetic field gradients on the development of the MRI: Applications to binary neutron star mergers and proto-planetary disks