Zonal Flows and Long-Distance Correlations during the Formation of the Edge Shear Layer in the TJ-II Stellarator Articles uri icon

publication date

  • April 2009

start page

  • 65007


  • 6


  • 51

International Standard Serial Number (ISSN)

  • 0741-3335

Electronic International Standard Serial Number (EISSN)

  • 1361-6587


  • A theoretical interpretation is given for the observed long-distance correlationsin potential fluctuations in TJ-II. The value of the correlation increases above the critical point of the transition for the emergence of the plasma edge shear flow layer. Mean (i.e. surface averaged, zero-frequency) sheared flows cannot account for the experimental results. A model consisting of four envelope equations for the fluctuation level, the mean flow shear, the zonal flow amplitude shear and the averaged pressure gradient is proposed. It is shown that the presence of zonal flows is essential to reproduce the main features of the experimental observations.