Modeling spatio-temporal nonlocality in mean-field dynamos

Abstract

When scale separation in space and time is poor, the alpha effect and turbulent diffusivity have to be replaced by integral kernels. Earlier work in computing these kernels using the test-field method is now generalized to the case in which both spatial and temporal scale separations are poor. The approximate form of the kernel is such that it can be treated in a straightforward manner by solving a partial differential equation for the mean electromotive force. The resulting mean-field equations are solved for oscillatory alpha-shear dynamos as well as alpha^2 dynamos in which alpha is antisymmetric about the equator, making this dynamo also oscillatory. In both cases, the critical values of the dynamo number is lowered by the fact that the dynamo is oscillatory.

7 pages, 3 figures, submitted to Astronomische Nachrichten

References in corpus (6)

• Mean-field concept and direct numerical simulations of rotating magnetoconvection and the geodynamo
• Kinematic alpha effect in isotropic turbulence simulations
• Scale dependence of alpha effect and turbulent diffusivity
• Memory effects in turbulent transport
• Turbulent diffusion with rotation or magnetic fields
• Magnetic helicity fluxes in interface and flux transport dynamos

Cited by in corpus (33)

• Current status of turbulent dynamo theory: From large-scale to small-scale dynamos
• Astrophysical hydromagnetic turbulence
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Stellar mixing length theory with entropy rain
• Galactic spiral patterns and dynamo action I: A new twist on magnetic arms
• Galactic Dynamos
• Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars
• Turbulent processes and mean-field dynamo
• Galactic Spiral Patterns and Dynamo Action II: Asymptotic Solutions
• Mean-field dynamo action from delayed transport
• Magnetic arms generated by multiple interfering galactic spiral patterns
• A mean field dynamo from negative eddy diffusivity
• Simulations of galactic dynamos
• Compressible test-field method and its application to shear dynamos
• Robustness of oscillatory ${\alpha }^2$ dynamos in spherical wedges
• Derivation and precision of mean field electrodynamics with mesoscale fluctuations
• Testing Alfvén wave propagation in a "realistic" set-up of the solar atmosphere
• On the spatial and temporal non-locality of dynamo mean-field effects in supersonic interstellar turbulence
• Non-locality of the Turbulent Electromotive Force
• Finite-time response of dynamo mean-field effects in magnetorotational turbulence
• Strong nonlocality variations in a spherical mean-field dynamo
• On the existence of shear-current effects in magnetized burgulence
• Negative magnetic eddy diffusivities from test-field method and multiscale stability theory
• Quantifying the effect of turbulent magnetic diffusion on the growth rate of the magneto-rotational instability
• Spatio-temporal non-localities in a solar-like mean-field dynamo
• The alpha-effect in a turbulent liquid-metal plane Couette flow
• Delayed Babcock-Leighton dynamos in the diffusion-dominated regime
• Mean-field closure parameters for passive scalar turbulence
• Helicity effect on turbulent passive and active scalar diffusivities
• Magnetic helicity fluxes in dynamos from rotating inhomogeneous turbulence
• Exploring helical dynamos with machine learning
• Advances in mean-field dynamo theories
• Non-linear and chaotic dynamo regimes