HIGH RAYLEIGH NUMBER BETA-CONVECTION

High resolution numerical simulations of thermal convection in a rapid ly rotating channel with gravity perpendicular to the rotation vector are described. The convecting columns are subject to a beta-effect res ulting from topographic vortex stretching. The symmetries of the probl em allow many invariant wavenumber sets, and this property is associat ed with the existence of stable multiple-equilibria at modest supercri ticality. The transition to chaotic behavior involves the production o f intermittent unstable orbits off a two-torus in energy space. At ver y high Rayleigh number (of order 10(6) to 10(7)) the motion can be tur bulent, depending on the size of beta. However, the turbulence is usua lly characterized by an almost-periodic formation of patches of small scale convection that cause regular pulsations in the accompanying str ong zonal jets. The processes maintaining these flows may be related t o those responsible for the zonal currents on Jupiter and for cyclic v ariability on the Sun.