Bifurcation and scaling of drift wave turbulence intensity with collisional zonal flow damping

Abstract

Interacting drift wave–zonal flow turbulence is examined at the spectral level of description using an extended “predator–prey” model. Analytic solutions that describe both the linear scaling of transport with ion–ion collisionality as well as the saturation regime are obtained for a simple model of drift wave turbulence. A theory of self-regulation in this system is presented. The possibility of bifurcation to a state with higher turbulence level and transport is demonstrated. This bifurcation is associated with the appearance of a condensate solution at the largest scales. The possible relevance of this phenomenon to the bursting events of turbulence and transport recently observed in gyrokinetic simulations of ITG instability is discussed.