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Magnetic field reversals in numerical simulations of the von Kármán sodium experiment

Rémi Bousquet1, Yannick Ponty2, Victor Botez1, Nicolas Plihon3, and Caroline Nore1

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Phys. Rev. Fluids 11, 063703 – Published 18 June, 2026

DOI: https://doi.org/10.1103/9tx2-1m13

Abstract

Numerical simulations and proper orthogonal decomposition are used to identify the fundamental mechanism of magnetic field reversals in the von Kármán sodium experiment with ferromagnetic impellers close to contrarotation. Two numerical solvers are used and agree well on the resulting mechanism. The reversal dynamics rely on the interaction of four dominant axisymmetric modes: the magnetic dipole mode D and quadrupole mode Q, as well as the zonal velocity mode V and the Rπ-symmetric mode U. This hierarchy leads to a reduced-order DQVU Galerkin model derived from the magnetohydrodynamic equations. The model improves upon previous three-variable versions by adding a velocity variable U and related interactions, which are shown to be essential for reproducing the main features of magnetic field dynamics.

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Outline

Information

Phys. Rev. Fluids 11, 063703– Published 18 June, 2026
  • Received 19 January 2026
  • Accepted 29 May 2026
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