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Morphology of field reversals in turbulent dynamos

Abstract : We show that the modes involved in the dynamics of reversals of the magnetic field generated by the flow of an electrically conducting fluid in a spherical domain, strongly depend on the magnetic Prandtl number Pm, i.e., the ratio between viscous and magnetic diffusivities. For Pm~1, the axial dipolar field reverses in the presence of a strong equatorial dipolar component, whereas for Pm<0.5, field reversals mostly involve axisymmetric modes, axial magnetic dipole and quadrupole coupled through a broken symmetry of the flow. Using symmetry arguments, we write a dynamical system for these three modes that qualitatively reproduces the main features of the reversals observed in direct simulations for small Pm.
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Submitted on : Friday, March 11, 2022 - 7:28:48 AM
Last modification on : Sunday, March 13, 2022 - 3:25:50 AM

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C. Gissinger, E. Dormy, S. Fauve. Morphology of field reversals in turbulent dynamos. EPL (Europhysics Letters), 2010, 90, pp.49001. ⟨10.1209/0295-5075/90/49001⟩. ⟨insu-03605331⟩

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