Statistical properties of transport in plasma turbulence

The statistical properties of the $E \times B$ flux in different types of plasma turbulence simulations are investigated using probability density distribution functions (PDF). The physics included in the models ranges from two dimensional drift-wave turbulence to three dimensional MHD simulations. The PDFs of the flux surface averaged transport are in good agreement with an extreme value distribution (EVD). This is interpreted as a signature of localized vortical structures dominating the transport on a flux surface. Models accounting for a local input of energy and including the global evolution of background profiles show a more bursty behavior in 2D as well as 3D simulations of interchange and drift type turbulence. Although the PDFs are not Gaussian, again no algebraic tails are observed. The tails are, in all cases considered, in excellent agreement with EVDs.