The generation of zonal flows and their interplay with drift wave turbulence is studied numerically using a model based on the Hasegawa–Mima equation, with an electron response depending only on the fluctuating part of the electrostatic potential. In regimes dominated by the diamagnetic velocity, large-amplitude nonlinear oscillations are observed in the time history of the zonal flow and drift wave spectra. Such oscillations have also recently been detected in toroidal gyrokinetic simulations, and could be important in determining the transport behavior in experimental devices.
