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Updated: Apr 20, 2026

Magnetically Induced Rotating Rayleigh-Taylor Instability
Published on: March 3, 2017
Turbulence reduces magnetic diffusivity in a liquid sodium experiment
Simon Cabanes1, Nathanaël Schaeffer1, Henri-Claude Nataf1
1Université Grenoble Alpes, ISTerre, F-38000 Grenoble, France and CNRS, ISTerre, F-38000 Grenoble, France.
Abstract:
The contribution of small scale turbulent fluctuations to the induction of a mean magnetic field is investigated in our liquid sodium spherical Couette experiment with an imposed magnetic field. An inversion technique is applied to a large number of measurements at Rm≈100 to obtain radial profiles of the α and β effects and maps of the mean flow. It appears that the small scale turbulent fluctuations can be modeled as a strong contribution to the magnetic diffusivity that is negative in the interior region and positive close to the outer shell. Direct numerical simulations of our experiment support these results. The lowering of the effective magnetic diffusivity by small scale fluctuations implies that turbulence can actually help to achieve self-generation of large scale magnetic fields.
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