Advances in theory and simulations of large-scale dynamos

Abstract

Recent analytical and computational advances in the theory of large-scale dynamos are reviewed. The importance of the magnetic helicity constraint is apparent even without invoking mean-field theory. The tau approximation yields expressions that show how the magnetic helicity gets incorporated into mean-field theory. The test-field method allows an accurate numerical determination of turbulent transport coefficients in linear and nonlinear regimes. Finally, some critical views on the solar dynamo are being offered and targets for future research are highlighted.

19 pages, 2 figures, to appear in Space Sci. Rev

References in corpus (48)

• Astrophysical magnetic fields and nonlinear dynamo theory
• The inverse cascade and nonlinear alpha-effect in simulations of isotropic helical hydromagnetic turbulence
• Global-Scale Turbulent Convection and Magnetic Dynamo Action in the Solar Envelope
• The case for a distributed solar dynamo shaped by near-surface shear
• Hydromagnetic turbulence in computer simulations
• Magnetic Helicity Conservation and Astrophysical Dynamos
• Mean-field concept and direct numerical simulations of rotating magnetoconvection and the geodynamo
• Dynamo Action in the Solar Convection Zone and Tachocline: Pumping and Organization of Toroidal Fields
• Dynamic nonlinearity in large scale dynamos with shear
• Magnetic diffusivity tensor and dynamo effects in rotating and shearing turbulence
• Numerical study of dynamo action at low magnetic Prandtl numbers
• Numerical demonstration of fluctuation dynamo at low magnetic Prandtl numbers
• The onset of a small-scale turbulent dynamo at low magnetic Prandtl numbers
• Large-scale dynamos in turbulent convection with shear
• Dynamical Quenching of the ${\alpha }^2$ Dynamo
• Turbulent magnetic Prandtl number and magnetic diffusivity quenching from simulations
• Kinematic alpha effect in isotropic turbulence simulations
• Local and nonlocal magnetic diffusion and alpha-effect tensors in shear flow turbulence
• Non-Fickian diffusion and tau approximation from numerical turbulence
• Scale dependence of alpha effect and turbulent diffusivity
• Alpha effect and turbulent diffusion from convection
• Magnetic helicity density and its flux in weakly inhomogeneous turbulence
• Minimal tau approximation and simulations of the alpha effect
• Nonlinear current helicity fluxes in turbulent dynamos and alpha quenching
• The Interaction of New and Old Magnetic Fluxes at the Beginning of Solar Cycle 23
• Magnetic helicity in stellar dynamos: new numerical experiments
• Simulation of induction at low magnetic Prandtl number
• Nonlinear magnetic diffusivity and alpha tensors in helical turbulence
• Large-scale Dynamo Action Driven by Velocity Shear and Rotating Convection
• Strong mean field dynamos require supercritical helicity fluxes
• Large scale dynamos with helicity loss through boundaries
• Large-scale dynamos in rigidly rotating turbulent convection
• Turbulent dynamos with shear and fractional helicity
• A New Approach to Turbulent Transport of a Mean Scalar
• Effect of Fractional Kinetic Helicity on Turbulent Magnetic Dynamo Spectra
• Alpha effect and diffusivity in helical turbulence with shear
• The helicity constraint in turbulent dynamos with shear
• Turbulent dynamos in spherical shell segments of varying geometrical extent
• A growing dynamo from a saturated Roberts flow dynamo
• Magnetic helicity effects in astrophysical and laboratory dynamos
• Kinetic and magnetic alpha effects in nonlinear dynamo theory
• Geodynamo alpha-effect derived from box simulations of rotating magnetoconvection
• Dynamical magnetic relaxation: A nonlinear magnetically driven dynamo
• The dual role of shear in large-scale dynamos
• Simulations of the anisotropic kinetic and magnetic alpha effects
• Mean-field effects in the Galloway-Proctor flow
• The helicity constraint in spherical shell dynamos
• Is there a phase constraint for solar dynamo models?

Cited by in corpus (19)

• Persistent Magnetic Wreaths in a Rapidly Rotating Sun
• Dynamo theories
• Microphysics of cosmic ray driven plasma instabilities
• Cosmic-ray current driven turbulence in shocks with efficient particle acceleration: the oblique, long-wavelength mode instability
• Global dynamo models from direct numerical simulations and their mean-field counterparts
• The inverse cascade of magnetic helicity in magnetohydrodynamic turbulence
• Characterising the Dynamo in a Radiatively Inefficient Accretion Flow
• Saturation and time dependence of geodynamo models
• Turbulent transport coefficients in galactic dynamo simulations using singular value decomposition
• Polar branches of stellar activity waves: dynamo models and observations
• The Magnetic Sun: Reversals and Long-Term Variations
• Not Much Helicity is Needed to Drive Large Scale Dynamos
• Turbulent dynamo action and its effects on the mixing at the convective boundary of an idealized oxygen-burning shell
• Turbulent 2.5 dimensional dynamos
• Role of helicities for the dynamics of turbulent magnetic fields
• Iterative removal of sources to model the turbulent electromotive force
• A study of large scale dynamo growth rates from numerical simulations and implications for mean field theories
• From convective to stellar dynamos
• On the Combined Role of Cosmic Rays and Supernova-Driven Turbulence for Galactic Dynamos