Streamer and zonal flow generation from envelope modulations in drift waveturbulence

The origin of anisotropic secondary flows, such as zonal flows and streamer s, in drift wave turbulence is examined, A unified description including di ffraction effects is given for zonal flow and streamer generation via envel ope modulation of drift-wave packet. Stability boundaries, nonlinear growth rates and typical structure scales are determined for both streamer and zo nal flow. A novel result is the determination of the characteristic width o f those structures. which is found to depend on intrinsically nonlinear pro cesses. (C) 2001 Elsevier Science B.V. All rights reserved.