A numerical model of the VKS experiment

TL;DR

This paper presents numerical simulations of magnetic field generation in the VKS experiment, showing how flow configurations influence magnetic modes, including reversals and oscillations.

Contribution

It introduces a dynamo kinematic model in cylindrical geometry that captures different magnetic modes based on flow symmetry and asymmetry.

Findings

Different magnetic modes depend on flow configuration.

Breaking flow symmetry induces oscillatory magnetic fields.

Reversals of magnetic polarity involve competition between dipolar and quadrupolar modes.

Abstract

We present numerical simulations of the magnetic field generated by the flow of liquid sodium driven by two counter-rotating impellers (VKS experiment). Using a dynamo kinematic code in cylindrical geometry, it is shown that different magnetic modes can be generated depending on the flow configuration. While the time averaged axisymmetric mean flow generates an equatorial dipole, our simulations show that an axial field of either dipolar or quadrupolar symmetry can be generated by taking into account non-axisymmetric components of the flow. Moreover, we show that by breaking a symmetry of the flow, the magnetic field becomes oscillatory. This leads to reversals of the axial dipole polarity, involving a competition with the quadrupolar component.