title: Nonlinear damping of plasma zonal flows excited by inverse spectral transfer.
abstract: Plasma zonal-flow excitation and saturation in fluid electron-drift-wave turbulence are studied spectrally. The zonal flow is a spectral condensation onto the zero-frequency linear-wave structure. In the representation diagonalizing the wave coupling that dominates interactions at long wavelengths, nonlinear triad interactions involving zero-frequency waves are greatly enhanced. Zonal modes are excited on both unstable and purely stable eigenmode branches. Coupling to the latter introduces robust, finite amplitude-induced damping of zonal flows, providing saturation.
authors.affiliation: Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA.
authors.forename: P W
authors.initials: PW
authors.lastname: Terry
authors.forename: R
authors.initials: R
authors.lastname: Gatto
authors.forename: D A
authors.initials: DA
authors.lastname: Baver