Due to the strong background magnetic field, turbulence in fusions plasmas has a 2-dimensional character. A fundamental property of 2D turbulence is the dual cascade. In contrast to 3D turbulence, where only a direct energy cascade is present, which transfers energy from large to small scales, in the 2D case energy is transported to large scales. At the same time, a direct enstrophy cascade leads to transport of eddy energy to small scales (see figure).
The dual turbulent cascade in drift-wave turbulence has been investigated experimentally and through simulations. A bispectral analysis technique has been applied to density and potential fluctuations on a 2-dimensional spatial grid. The basis of the model is the transfer of energy through 3-wave interaction. The experimental data were obtained with the matrix array. For the first time, evidence for the dual turbulent cascade has been obtained from spatially resolved experimental data
Mirko Ramisch
Dr.Head of Plasma Dynamics and Diagnostics / Library officer