Magnetic structure, dipole reversals, and 1/f noise in resistive MHD spherical dynamos

Abstract

A parametric study of the magnetic dipole behavior in resistive incompressible MHD inside a rotating sphere is performed, using direct numerical simulations and considering Reynolds and Ekman numbers as controlling parameters. The tendency is to obtain geodynamo-like magnetic dipole reversal regimes for sufficiently small Ekman and large Reynolds numbers. The typical dipole latitude obtained in the reversal regime is around 40 degrees (with respect to the rotation axis of the sphere). A statistical analysis of waiting times between dipole reversals is also performed, obtaining a non-Poissonian distribution of waiting times, indicating long-term memory effects. We also report the presence of a $1/f$ frequency power spectrum in the magnetic dipole time-series, which also shows a tendency to grow toward lower frequencies as the Ekman number is decreased.

arXiv comment14 pages, 9 figures

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Cited by in corpus (4)

• Fourier continuation method for incompressible fluids with boundaries
• Vector potential-based MHD solver for non-periodic flows using Fourier continuation expansions
• Effect of electromagnetic boundary conditions on the onset of small-scale dynamos driven by convection
• Behavior of hydrodynamic and magnetohydrodynamic turbulence in a rotating sphere with precession and dynamo action