Numerical experiments on dynamo action in sheared and rotating turbulence

Abstract

Numerical simulations of forced turbulence in elongated shearing boxes are carried out to demonstrate that a nonhelical turbulence in conjunction with a linear shear can give rise to a mean-field dynamo. Exponential growth of magnetic field at scales larger than the outer (forcing) scale of the turbulence is found. Over a range of values of the shearing rate S spanning approximately two orders of magnitude, the growth rate of the magnetic field is proportional to the imposed shear, gamma ~ S, while the characteristic spatial scale of the field is l_b ~ S^(-1/2). The effect is quite general: earlier results for the nonrotating case by Yousef et al. 2008 (PRL 100, 184501) are extended to shearing boxes with Keplerian rotation; it is also shown that the shear dynamo mechanism operates both below and above the threshold for the fluctuation dynamo. The apparently generic nature of the shear dynamo effect makes it an attractive object of study for the purpose of understanding the generation of magnetic fields in astrophysical systems.

13 pages, 10 figures, version published in Astronomische Nachrichten

References in corpus (37)

• Astrophysical magnetic fields and nonlinear dynamo theory
• The inverse cascade and nonlinear alpha-effect in simulations of isotropic helical hydromagnetic turbulence
• Simulations of small-scale turbulent dynamo
• Enhanced Angular Momentum Transport in Accretion Disks
• The case for a distributed solar dynamo shaped by near-surface shear
• Simulations of nonhelical hydromagnetic turbulence
• Hydrodynamic turbulence cannot transport angular momentum effectively in astrophysical disks
• MHD simulations of the magnetorotational instability in a shearing box with zero net flux. II. The effect of transport coefficients
• Impact of dimensionless numbers on the efficiency of MRI-induced turbulent transport
• The magnetic field of the Large Magellanic Cloud revealed through Faraday rotation
• Magnetic diffusivity tensor and dynamo effects in rotating and shearing turbulence
• Numerical study of dynamo action at low magnetic Prandtl numbers
• 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
• Direct simulations of a supernova-driven galactic dynamo
• On the relevance of subcritical hydrodynamic turbulence to accretion disk transport
• Numerical demonstration of fluctuation dynamo 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
• Generation of Magnetic Field by Combined Action of Turbulence and Shear
• A self-sustaining nonlinear dynamo process in Keplerian shear flows
• On Self-Sustained Dynamo Cycles in Accretion Discs
• The mean electromotive force due to turbulence of a conducting fluid in the presence of mean flow
• Scale by scale budget and similarity laws for shear turbulence
• Nonlinear magnetic diffusivity and alpha tensors in helical turbulence
• Effects of fluctuation on alpha-omega dynamo models
• Magnetic Fields and Ionized Gas in the Local Group Irregular Galaxies IC10 and NGC6822
• Effect of Fractional Kinetic Helicity on Turbulent Magnetic Dynamo Spectra
• On self-sustaining processes in Rayleigh-stable rotating plane Couette flows and subcritical transition to turbulence in accretion disks
• Generation of Large-Scale Vorticity in a Homogeneous Turbulence with a Mean Velocity Shear
• Nonlinear Evolution of Hydrodynamical Shear Flows in Two Dimensions
• In Situ Origin of Large Scale Galactic Magnetic Fields Without Kinetic Helicity?
• Mean-field dynamo in a turbulence with shear and kinetic helicity fluctuations
• Non-normal and Stochastic Amplification in Turbulent Dynamo: Subcritical Case
• Generation of the magnetic field in jets
• Magnetic Fields in Irregular Galaxies

Cited by in corpus (34)

• Dynamo theories
• Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
• Astrophysical turbulence modeling
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Large-Scale Magnetic-Field Generation by Randomly Forced Shearing Waves
• Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection
• Large-scale dynamos in rigidly rotating turbulent convection
• Turbulent dynamos with shear and fractional helicity
• Generation of large-scale magnetic fields by small-scale dynamo in shear flows
• Dynamo action and magnetic buoyancy in convection simulations with vertical shear
• Numerical study of large-scale vorticity generation in shear-flow turbulence
• On Large-Scale Dynamo Action at High Magnetic Reynolds Number
• The shear dynamo problem for small magnetic Reynolds numbers
• The alpha effect in rotating convection with sinusoidal shear
• Pumping velocity in homogeneous helical turbulence with shear
• Nonperturbative quasilinear approach to the shear dynamo problem
• Transport coefficients for the shear dynamo problem at small Reynolds numbers
• Dynamo Action in a Quasi-Keplerian Taylor-Couette Flow
• The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo
• Shear dynamo problem: Quasilinear kinematic theory
• Coherent nonhelical shear dynamos driven by magnetic fluctuations at low Reynolds numbers
• Shear Acceleration in Expanding Flows
• The Elemental Shear Dynamo
• The Effect of Velocity Shear on Dynamo Action Due to Rotating Convection
• Numerical studies of dynamo action in a turbulent shear flow - I
• On the existence of shear-current effects in magnetized burgulence
• On the shear-current effect: toward understanding why theories and simulations have mutually and separately conflicted
• Quantifying the effect of turbulent magnetic diffusion on the growth rate of the magneto-rotational instability
• Mean field dynamo action in renovating shearing flows
• Mean field dynamo action in shearing flows. II: fluctuating kinetic helicity with zero mean
• Generation of large-scale magnetic fields due to fluctuating $\alpha$ in shearing systems
• Vorticity and magnetic dynamo from subsonic expansion waves
• Effect of flow shear on the onset of dynamos
• From convective to stellar dynamos