Catastrophic quenching in alpha-Omega dynamos revisited

Abstract

At large magnetic Reynolds numbers, magnetic helicity evolution plays an important role in astrophysical large-scale dynamos. The recognition of this fact led to the development of the dynamical alpha quenching formalism, which predicts catastrophically low mean fields in open systems. Here we show that in oscillatory alpha-Omega dynamos this formalism predicts an unphysical magnetic helicity transfer between scales. An alternative technique is proposed where this artifact is removed by using the evolution equation for the magnetic helicity of the total field in the shearing--advective gauge. In the traditional dynamical alpha quenching formalism, this can be described as an additional magnetic helicity flux of small-scale fields that does not appear in homogeneous alpha-squared dynamos. In alpha-Omega dynamos, the alternative formalism is shown to lead to larger saturation fields than previously obtained with the traditional formalism.

9 pages, 7 figures, Published, ApJ

References in corpus (13)

• Mean-field concept and direct numerical simulations of rotating magnetoconvection and the geodynamo
• Kinematic alpha effect in isotropic turbulence simulations
• Scale dependence of alpha effect and turbulent diffusivity
• Equatorial magnetic helicity flux in simulations with different gauges
• Nonlinear magnetic diffusivity and alpha tensors in helical turbulence
• Strong mean field dynamos require supercritical helicity fluxes
• Catastrophic alpha quenching alleviated by helicity flux and shear
• Test-field method for mean-field coefficients with MHD background
• Magnetic helicity fluxes in an alpha-squared dynamo embedded in a halo
• The alpha effect with imposed and dynamo-generated magnetic fields
• Magnetic helicity transport in the advective gauge family
• Magnetic helicity flux in the presence of shear
• Shear-driven and diffusive helicity fluxes in alpha-Omega dynamos

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