  Intermittent fluctuations in the boundary of magnetically confined plasmas
are investigated by numerical turbulence simulations of a reduced fluid model
describing the evolution of the plasma density and electric drift vorticity in
the two-dimensional plane perpendicular to the magnetic field. Two different
cases are considered, one describing resistive drift waves in the edge region
and another including only the interchange instability due to unfavorable
magnetic field curvature in the scrape-off layer. Analysis of long data time
series obtained by single-point recordings are compared to predictions of a
stochastic model describing the plasma fluctuations as a super-position of
uncorrelated pulses. For both cases investigated, the radial particle density
profile in the scrape-off layer is exponential with a radially constant scale
length. The probability density function for the particle density fluctuations
in the far scrape-off layer has an exponential tail. Radial motion of blob-like
structures leads to large-amplitude bursts with an exponential distribution of
peak amplitudes and the waiting times between them. The average burst shape is
well described by a two-sided exponential function. The frequency power
spectral density of the particle density is simply that of the average burst
shape and is the same for all radial positions in the scrape-off layer. The
fluctuation statistics obtained from the numerical simulations are in excellent
agreement with recent experimental measurements on magnetically confined
plasmas. The statistical framework defines a new validation metric for boundary
turbulence simulations.
