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 analog of the "shear-current" effect. In addition, consideration of α effects in the stratified regions of disks gives the puzzling result that there is no strong prediction for a sign of α , 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.

Additional Information

© 2015 American Physical Society. Received 6 August 2015; published 2 November 2015. This work was supported by a Procter Fellowship at Princeton University and U.S. Department of Energy Grant No. DE-AC02-09-CH11466. The authors would like to thank I. Rogachevskii, A. Schekochihin, and J. Krommes for enlightening discussion and useful suggestions.

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Published - PhysRevE.92.053101.pdf

Supplemental Material - SOCAcalculation.nb

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