  Recently, it has been proposed that the turbulent fluctuations measured in a
linear plasma device could be described as a superposition of uncorrelated
Lorentzian pulses with a narrow distribution of durations, which would provide
an explanation for the reported quasi-exponential power spectra. Here, we study
the applicability of this proposal to edge fluctuations in toroidal magnetic
confinement fusion plasmas. For the purpose of this analysis, we introduce a
novel wavelet-based pulse detection technique that offers important advantages
over existing techniques. It allows extracting the properties of individual
pulses from the experimental time series, and quantifying the distribution of
pulse duration and energy, as well as temporal correlations.
  We apply the wavelet technique to edge turbulent fluctuation data from the
W7-AS stellarator and the JET tokamak, and find that the pulses detected in the
data do not have a narrow distribution of durations and are not uncorrelated.
Instead, the distributions are of the power law type, exhibiting temporal
correlations over scales much longer than the typical pulse duration. These
results suggest that turbulence in open and closed field line systems may be
distinct and cast doubt on the proposed ubiquity of exponential power spectra
in this context.
