Characterization of intermittency in plasma edge turbulence

The intermittency in the edge turbulence of the magnetic confinement devices, caused by large-scale events with high radial velocity, has been the object of several recent studies. It is well known that bursty behavior in the scrape-off layer of magnetically confined plasmas, and the departure from random diffusion models is caused by intermittent large-scale plasma structures radially convected at high speed. Recently performed statistical analysis of plasma density fluctuations have demonstrated universal features of intermittent phenomena in plasma turbulence in the sense that they originate and have the same properties in many devices with distinct configurations. We extend the universal features of turbulence to Laplace distributions of derivatives of plasma density flucutations and show the properties of distributions for various confinement regimes. We further demonstrate that universal features are not complete by performing multifractal analysis which reveals unique features for each device and for each confinement regime. (c) 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim