Enhanced dynamo growth in nonhomogeneous conducting fluids

Abstract

We address magnetic-field generation by dynamo action in systems with inhomogeneous electrical conductivity and magnetic permeability. More specifically, we first show that the Taylor-Couette kinematic dynamo undergoes a drastic reduction of its stability threshold when a (zero-mean) modulation of the fluid's electrical conductivity or magnetic permeability is introduced. These results are obtained outside the mean-field regime, for which this effect was initially proposed. Beyond this illustrative example, we extend a duality argument put forward by Favier \& Proctor {(2013)} to show that swapping the distributions of conductivity and permeability and changing $u\to -u$ leaves the dynamo threshold unchanged. This allows one to make connections between {\it a priori} unrelated dynamo studies. Finally, we discuss the possibility of observing such an effect both in laboratory and astrophysical settings.

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Cited by in corpus (3)

• Fast and Furious dynamo action in the anisotropic dynamo
• On the toroidal-velocity anti-dynamo theorem under the presence of nonuniform electric conductivity
• Effects of radial conductivity variation on the Ponomarenko dynamo