Large-scale dynamo produced by negative magnetic eddy diffusivities
Résumé
The existence of incompressible flow producing negative magnetic eddy diffusivities is demonstrated. This provides for a dynamo mechanism, alternative to α-type effects, requiring neither the presence of mean heliciiy nor the breaking of parity invariance. In the kinematic dynamo phase, the magnetic field grows exponentially with a growth rate proportional to the square of the wavenumber. The concrete example, analyzed by means of multiscale techniques, is a parity-invariant flow of the Taylor-Green type.
Domaines
Océan, Atmosphère
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