Electromotive force due to magnetohydrodynamic fluctuations in sheared rotating turbulence

Abstract

This article presents a calculation of the mean electromotive force arising from general small-scale magnetohydrodynamical turbulence, within the framework of the second-order correlation approximation. With the goal of improving understanding of the accretion disk dynamo, effects arising through small-scale magnetic fluctuations, velocity gradients, density and turbulence stratification, and rotation, are included. The primary result, which supplements numerical findings, is that an off-diagonal turbulent resistivity due to magnetic fluctuations can produce large-scale dynamo action -- the magnetic analogue of the "shear-current" effect. In addition, consideration of $\alpha$ effects in the stratified regions of disks gives the puzzling result that there is no strong prediction for a sign of $\alpha$, since the effects due to kinetic and magnetic fluctuations, as well as those due to shear and rotation, are each of opposing signs and tend to cancel each other.

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Cited by in corpus (20)

• Dynamo theories
• Advances in mean-field dynamo theory and applications to astrophysical turbulence
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• Large scale dynamo action precedes turbulence in shearing box simulations of the magnetorotational instability
• The magnetic shear-current effect: generation of large-scale magnetic fields by the small-scale dynamo
• Magnetorotational instability with smoothed particle hydrodynamics
• Simulating the magnetorotational instability on a moving mesh with the shearing box approximation
• Motivation and challenge to capture both large scale and local transport in next generation accretion theory
• Radially Dependent Large Scale Dynamos in Global Cylindrical Shear Flows and the Local Cartesian Limit
• Non-linear Galactic Dynamos and the Magnetic Rädler Effect
• Interaction of large- and small-scale dynamos in isotropic turbulent flows from GPU-accelerated simulations
• On large-scale dynamos with stable stratification and the application to stellar radiative zones
• 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
• A new constraint on mean-field galactic dynamo theory
• Unified treatment of mean-field dynamo and angular-momentum transport in magnetorotational instability-driven turbulence
• Magnetic helicity fluxes in dynamos from rotating inhomogeneous turbulence
• Helical and nonhelical large-scale dynamos in thin accretion discs
• Electromotive field in space and astrophysical plasmas
• Turbulence and order in magnetized flowing plasmas