Turbulence Reduces Magnetic Diffusivity in a Liquid Sodium Experiment

Abstract

The contribution of small scale turbulent fluctuations to the induction of 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 $Rm\approx 100$ to obtain radial profiles of the $\alpha$ and $\beta$ 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.

Rajout d'un erratum

References in corpus (8)

• Efficient Spherical Harmonic Transforms aimed at pseudo-spectral numerical simulations
• Scale dependence of alpha effect and turbulent diffusivity
• Zonal shear and super-rotation in a magnetized spherical Couette flow experiment
• Modes and instabilities in magnetized spherical Couette flow
• Turbulence Reduces Magnetic Diffusivity in a Liquid Sodium Experiment
• Magnetic induction maps in a magnetized spherical Couette flow experiment
• Magnetic induction and diffusion mechanisms in a liquid sodium spherical Couette experiment
• Magnetic material in mean-field dynamos driven by small scale helical flows

Cited by in corpus (8)

• Turbulence Reduces Magnetic Diffusivity in a Liquid Sodium Experiment
• Convection-driven kinematic dynamos at low Rossby and magnetic Prandtl numbers: single mode solutions
• Magnetic induction and diffusion mechanisms in a liquid sodium spherical Couette experiment
• Negative magnetic eddy diffusivities from test-field method and multiscale stability theory
• Can Core Flows inferred from Geomagnetic Field Models explain the Earth's Dynamo?
• Magnetic fields in circumstellar envelopes of evolved AGB stars
• Fluid Dynamics of Earth's core: geodynamo, inner core dynamics, core formation
• $\alpha$ Effect and Magnetic Diffusivity $\beta$ in Helical Plasma under Turbulence Growth