Statistical analysis of turbulent front propagation in the scrape-off-layer

The intermittent transport in the SOL is analysed in terms of the interaction between the average profile and the population of large transport events, the fronts. This provides the basis for the statistical analysis presented in this paper. Data from 2D numerical simulations is analysed here. The mean density e-folding length for the fronts is observed to be the same as that of the time average profile. The mean ballistic velocity of the fronts has a radial Mach number of 0.03. A symmetric distribution of poloidal Mach numbers is found, its width is comparable to that of the radial Mach number, Delta M similar to 0.02. The small fronts are found to be isotropic, the larger fronts are elongated radially (aspect ratio similar to 6). A characteristic poloidal scale is found, typically 7 Larmor radii. (c) 2004 Elsevier B.V. All rights reserved.