Streamer saturation: a dynamical systems approach

Small-scale turbulence in toroidal magnetoplasmas driven by electron or ion temperature gradient modes is known for its tendency to form strongly anisotropic structures, namely radially elongated vortices called streamers or (mostly) poloidal E×BE×B shear flows called zonal flows. The interaction of such patterns is studied here in the framework of a simple dynamical system, focusing in particular on the initial saturation phase of a streamer. It is shown that the saturation amplitude, in this reduced description, is determined by a balance between the streamer's linear growth rate and the zonal mode's nonlinear growth rate.