A global nonlinear stability analysis is performed for a couple-stress fluid layer heated from below saturating a porous medium with temperature-pressure dependent viscosity for different conducting boundary systems. Here, the global nonlinear stability threshold for convection is exactly the same as the linear instability boundary. This optimal result is important because it shows that lineari...

Recent investigations into convection in Europa’s ice shell have been based on nonNewtonian (stress-dependent) or Newtonian (stress-independent) viscosity for water ice. However, despite the wide use of Newtonian convection, experimentally observed water ice flow is non-Newtonian, and analysis of stability against convection of the ice shell using updated flow laws has been only performed for n...

[1] The ‘‘transition zone water filter’’ model of mantle convection attempts to reconcile geochemical evidence for isolated mantle reservoirs with geophysical evidence for whole mantle circulation by decoupling incompatible elements from bulk mantle circulation via a melt layer above the 410 km discontinuity. This would result in a stratified heating distribution similar to layered convection m...

We report experimental measurements of heat transport in rotating Rayleigh-Bénard convection in a cylindrical convection cell with an aspect ratio of Γ=1/2. The fluid is helium gas with a Prandtl number Pr=0.7. The range of control parameters for Rayleigh numbers 4×10^{9}<Ra<4×10^{11} and for Ekman numbers 2×10^{-7}<Ek<3×10^{-5} (corresponding to Taylor numbers 4×10^{9}<Ta<1×10^{14} and convect...

[1] We investigate the physics of multiscale convection in Earth’s mantle, characterized by the coexistence of large-scale mantle circulation associated with plate tectonics and small-scale sublithospheric convection. In this study, conditions for the existence of smallscale convection beneath oceanic lithosphere are investigated by deriving a scaling law for the onset of convection in a fluid ...

The onset of convection in the power-law creep regime on the terrestrial planets and icy satellites is poorly constrained. The major difficulty is that the viscosity of power-law fluids approaches infinity when the perturbation amplitudes approach zero and thus the methods of linear theory are inapplicable. Here, we determine the critical Rayleigh number for the onset of convection by starting ...

We perform numerical simulations in 3D spherical geometry to study the properties of convection in Europa’s silicate mantle using the finite-element code CitcomS including temperature-dependent viscosity. Our simulations show that thermal convection occurs if the reference viscosity is – PaS, rheological activation energy is 150-300 kJ/mol, and the viscosity contrast (due to temperature variati...

We couple two-dimensional hydrodynamics to detailed one-dimensional multigroup ux-limited diiusion neutrino transport to investigate prompt convection in core collapse supernovae. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement mu...