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