Nonlinear damping of plasma zonal flows excited by inverse spectral transfer.
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.
Terry
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PW
Department of Physics, University of Wisconsin-Madison, Madison, WI 53706, USA.
Gatto
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R
Baver
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DA