title: In search of the elusive zonal flow using cross-bicoherence analysis
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 L-->H transition near the edge shear layer indicate a modification in the nonlinear phase coupling, which might be linked to the generation of sheared ExB flows.
authors.affiliation: University of California, San Diego, La Jolla, California 92093-0319, USA.
authors.initials: PH
authors.lastname: Diamond
authors.initials: MN
authors.lastname: Rosenbluth
authors.initials: E
authors.lastname: Sanchez
authors.initials: C
authors.lastname: Hidalgo
authors.lastname: Van Milligen B
authors.initials: T
authors.lastname: Estrada
authors.initials: B
authors.lastname: Branas
authors.initials: M
authors.lastname: Hirsch
authors.initials: HJ
authors.lastname: Hartfuss
authors.initials: BA
authors.lastname: Carreras