  A new, frequency modulation mechanism for zonal flow pattern formation is
presented. The model predicts the probability distribution function of the flow
strength as well as the evolution of the characteristic spatial scale. Magnetic
toroidicity-induced global phase dynamics is shown to determine the spatial
structure of the flow. A key result is the observation that global phase
patterning can lead to zonal flow formation in the absence of turbulence
inhomogeneity.
