Non-locality of the Turbulent Electromotive Force

Abstract

The generation of large-scale magnetic fields ($\overline{\mathbf{B}}$) in astrophysical systems is driven by the mean turbulent electromotive force ($\overline{\mathcal{E}}$), the cross correlation between local fluctuations of velocity and magnetic fields. This can depend non-locally on $\overline{\mathbf{B}}$ through a convolution kernel $K_{ij}$. In a new approach to find $K_{ij}$, we directly fit the time series data of $\overline{\mathcal{E}}$ versus $\overline{\mathbf{B}}$ from a galactic dynamo simulation using singular value decomposition. We calculate the usual turbulent transport coefficients as moments of $K_{ij}$, show the importance of including non-locality over eddy length scales to fully capture their amplitudes and that higher order corrections to the standard transport coefficients are small in the present case.

arXiv comment11 pages, 13 figures

References in corpus (25)

• Astrophysical magnetic fields and nonlinear dynamo theory
• Cosmological Non-Linearities as an Effective Fluid
• Mean-field concept and direct numerical simulations of rotating magnetoconvection and the geodynamo
• A New Dynamical Mean-Field Dynamo Theory and Closure Approach
• Direct simulations of a supernova-driven galactic dynamo
• Kinematic alpha effect in isotropic turbulence simulations
• The Mean Electromotive Force for MHD Turbulence: the Case of a Weak Mean Magnetic Field and Slow Rotation
• Local and nonlocal magnetic diffusion and alpha-effect tensors in shear flow turbulence
• Scale dependence of alpha effect and turbulent diffusivity
• Alpha effect and turbulent diffusion from convection
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
• Memory effects in turbulent transport
• Characterizing the mean-field dynamo in turbulent accretion disks
• Turbulence and its parameterization in accretion discs
• Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars
• Modeling spatio-temporal nonlocality in mean-field dynamos
• A unified large/small-scale dynamo in helical turbulence
• Characterisation of the turbulent electromotive force and its magnetically-mediated quenching in a global EULAG-MHD simulation of solar convection
• Dynamo saturation in direct simulations of the multi-phase turbulent interstellar medium
• Supernova-regulated ISM -- V. Space- and time-correlations
• Characterising the Dynamo in a Radiatively Inefficient Accretion Flow
• Turbulent transport coefficients in galactic dynamo simulations using singular value decomposition
• On the spatial and temporal non-locality of dynamo mean-field effects in supersonic interstellar turbulence
• Passive scalar mixing and decay at finite correlation times in the Batchelor regime
• Mean-field dynamos: the old concept and some recent developments

Cited by in corpus (2)

• Galactic Dynamos
• Turbulent radiative diffusion and turbulent Newtonian cooling