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.

11 pages, 13 figures

References in corpus (6)

• Mean-field concept and direct numerical simulations of rotating magnetoconvection and the geodynamo
• Direct simulations of a supernova-driven galactic dynamo
• Kinematic alpha effect in isotropic turbulence simulations
• Scale dependence of alpha effect and turbulent diffusivity
• Alpha effect and turbulent diffusion from convection
• Memory effects in turbulent transport

Cited by in corpus (2)

• Galactic Dynamos
• Turbulent radiative diffusion and turbulent Newtonian cooling