Nonlinear α‐Effect in Dynamo Theory

Abstract
The standard two-scale theory of the dynamo coefficient α in incompressible isotropic helical MHD turbulence is extended to include nonlinear effects of , the large-scale magnetic field. We express α in terms of statistical quantities that can be calculated from numerical simulations of the case =0. For large magnetic Reynolds numbers, our formula agrees approximately with that of Kraichnan but disagrees with that of Cattaneo & Hughes.
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