Onset of convection in internally heated fluids with strongly temperature-dependent viscosity

We investigate the onset of convection in internally heated fluids with strongly temperature-dependent viscosity by solving numerically a non-linearized system of thermal convection equations in two dimensions for viscosity contrasts up to similar to 10(35.) As the viscosity contrast increases, a high-viscosity stagnant lid develops at the upper surface and convection occurs in a sublayer beneath it. The transition to stagnant-lid convection occurs at about the same viscosity contrast as in Rayleigh-Benard convection. We obtain asymptotic scaling relationships for the critical Rayleigh number and other parameters in the stagnant-lid regime. We also investigated the possibility of subcritical convection. In contrast to the Rayleigh-Benard problem, we did not detect a subcritical region for internally heated convection in twodimensional simulations. The results of this study can help improve our understanding of the conditions under which convection occurs in planetary interiors. Published under an exclusive license by AIP Publishing.

Automated summary

We investigate the onset of convection in internally heated fluids with strongly temperature-dependent viscosity. As the viscosity contrast increases, a high-viscosity stagnant lid develops at the upper surface and convection occurs in a sublayer beneath it. The results of this study can help improve our understanding of the conditions under which convection occurs in planetary interiors.