Thermochemical convection in a slowly rotating spherical shell: a transition between prograde and retrograde flows

Abstract

We numerically investigate thermochemically-driven convection in a spherical shell at a high Ekman number for a range of Rayleigh numbers, Prandtl numbers and buoyancy ratios. Rotating convection displays a nearly axisymmetric large-scale structure and appears mostly unaffected by the nature (thermal or chemical) of the driving buoyancy source. We observe both precession directions, prograde and retrograde, of convection structures and identify a snap-through transition between the prograde and retrograde flows in the parameter space spanned by the Rayleigh and Prandtl numbers. Equatorially wall-attached and spiralling columnar convection structures, which typically emerge in rapidly rotating shells, are not observed.

Keywords:

• Spherical shells
• thermochemical convection
• codensity formulation
• prograde flows
• retrograde flows

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study was supported by the VEGA grant 1/0245/24, the Mobility Project SAV-23-06/CAS-SAS-2022-01 and the Comenius University Grant UK/1170/2024. Computing resources (the SGI cluster NEMO) supporting this work were provided by the institute of Geophysics at the Czech Academy of Sciences.