In search of the elusive zonal flow using cross-bicoherence analysis
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.
Diamond
PH
University of California, San Diego, La Jolla, California 92093-0319, USA.
Rosenbluth
MN
Sanchez
E
Hidalgo
C
Van Milligen B
Estrada
T
Branas
B
Hirsch
M
Hartfuss
HJ
Carreras
BA