Abstract
We show that the modulational instability growth rate of zonal flows is determined directly from the quasilinear wave kinetic equation. We also demonstrate the relation between zonal-flow growth and the cross bispectrum of the high-frequency drift-wave-driven Reynolds stress and the low-frequency plasma potential by explicit calculation. Experimental measurements of the spatiotemporal evolution of the spectrum integrated bicoherence at the transition near the edge shear layer indicate a modification in the nonlinear phase coupling, which might be linked to the generation of sheared flows.
- Received 27 December 1999
DOI:https://doi.org/10.1103/PhysRevLett.84.4842
©2000 American Physical Society