Direct Measurement of Effective Magnetic Diffusivity in Turbulent Flow of Liquid Sodium

TL;DR

This study provides the first direct measurements of effective magnetic diffusivity in turbulent liquid sodium flow at high magnetic Reynolds numbers, revealing significant deviations from laminar values.

Contribution

It introduces a novel experimental approach to directly measure magnetic diffusivity in turbulent conductive fluids at high Rm.

Findings

Magnetic diffusivity deviates up to 50% from laminar values in turbulent flow.

Effective magnetic diffusivity measured at Rm ≈ 30.

First direct measurement of beta-effect in liquid sodium turbulence.

Abstract

The first direct measurements of effective magnetic diffusivity in turbulent flow of electro-conductive fluids (the so-called beta-effect) under magnetic Reynolds number Rm >> 1 are reported. The measurements are performed in a nonstationary turbulent flow of liquid sodium, generated in a closed toroidal channel. The peak level of the Reynolds number reached Re \approx 3 10^6, which corresponds to the magnetic Reynolds number Rm \approx 30. The magnetic diffusivity of the liquid metal was determined by measuring the phase shift between the induced and the applied magnetic fields. The maximal deviation of magnetic diffusivity from its basic (laminar) value reaches about 50% .