The eddy heat-flux in rotating turbulent convection

The three components of the heat-flux vector F = ρCp〈uT 〉 are numerically computed for a stratified rotating turbulent convection using the NIRVANA code in a flat box. The latitudinal component Fθ proves to be negative (positive) in the northern (southern) hemisphere so that the heat always flows towards the poles. As a surprise, the radial heat-flux Fr peaks at the equator rather than at the poles (Taylor numbers O(106)). The same behavior is observed for the radial turbulence intensity 〈u r 〉 which for free turbulence is also believed to peak at the poles (see Eq. (19) below). As we can show, however, the consequences of this unexpected result (also obtained by Käpylä, Korpi & Tuominen 2004) for the theory of differential rotation are small as mainly the Fθ is responsible to solve the ‘Taylor number puzzle’. In all our simulations the azimuthal component Fφ proves to be negative so that the rotating turbulence produces an westwards directed azimuthal heat-flux which should be observable. Fluctuations with higher temperature are expected to be anticorrelated with their own angular velocity fluctuations. We find this rotation-induced result as understandable as the Fφ is closely related to the radial Λ-effect which is known to be also negative in stratified and rapidly rotating convection zones.