Sensitivity to luminosity, centrifugal force, and boundary conditions in spherical shell convection

Abstract

We test the sensitivity of hydrodynamic and magnetohydrodynamic turbulent convection simulations with respect to Mach number, thermal and magnetic boundary conditions, and the centrifugal force. We find that varying the luminosity, which also controls the Mach number, has only a minor effect on the large-scale dynamics. A similar conclusion can also be drawn from the comparison of two formulations of the lower magnetic boundary condition with either vanishing electric field or current density. The centrifugal force has an effect on the solutions, but only if its magnitude with respect to acceleration due to gravity is by two orders of magnitude greater than in the Sun. Finally, we find that the parameterisation of the photospheric physics, either by an explicit cooling term or enhanced radiative diffusion, is more important than the thermal boundary condition. In particular, runs with cooling tend to lead to more anisotropic convection and stronger deviations from the Taylor-Proudman state. In summary, the fully compressible approach taken here with the Pencil Code is found to be valid, while still allowing the disparate timescales to be taken into account.

26 pages, 14 figures, accepted to GAFD Special issue on 'Physics and Algorithms of the Pencil Code'

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• Stellar dynamos in the transition regime: multiple dynamo modes and anti-solar differential rotation
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• Physically motivated heat conduction treatment in simulations of solar-like stars: effects on dynamo transitions
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• Origin of eclipsing time variations in Post-Common-Envelope binaries: role of the centrifugal force
• The time step constraint in radiation hydrodynamics
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• Shaping core dynamos in A-type stars: The role of dipolar fossil fields
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• Ill-posedness of the mean-field dynamo equations with a linear electromotive force