Streamer and zonal flow generation from envelope modulations in drift wave turbulence

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