Zonal flow driven by deep convection in the major planets

Tile cause of the fast zonal winds on the large gas planets is disputed. To investigate their possible origin by convection in the planets' molecular hydrogen layer, I study simple numerical models of thermal convection in a rotating sphere at low Ekman numbers for Rayleigh numbers up to 100 times c ritical. With stress-free boundaries and high Rayleigh number it is possibl e to reproduce the observed magnitudes of tile zonal and non-zonal flow com ponents at the surfaces of Jupiter and Saturn. While only three flow bands are found for a thick convecting shell, the number increases to seven for a shell with an inner-to-outer radius of 0.6.