Multiresolution analysis of the two-dimensional free decaying turbulence in a pure electron plasma

The two-dimensional (2D) freely decaying turbulence is investigated experimentally in an electron plasma confined in a Malmberg-Penning trap and studied using a wavelet-based multiresolution analysis. The coherent and incoherent parts of the flow are extracted using a recursive denoising algorithm with an adaptive self-consistent threshold. Only a small number of wavelet coefficients (but corresponding to the greatest part of the enstrophy or energy contents) turns out to be necessary to represent the coherent component. The remaining small amplitude coefficients represent the incoherent component, which is characterized by a near Gaussian vorticity PDF. Scale contributions to the measured enstrophy and energy distributions are inferred, and the results are compared with recent experiments and theoretical pictures of the 2D turbulence. The results suggest that the computational complexity of 2D turbulent flows may be reduced in simulations by considering only coherent structures interacting with a statistically modeled background.