  Analysis of the time series obtained with the O-Mode reflectometer (Rhodes et
al 1997 Plasma Phys. and Control. Fusion 40 (1998) 493-510) and the gas puff
imaging (Cziegler, I. et al 2010 Phys. of Plasmas 17, No. 5 (2010) 056120)
systems on the Alcator C-Mod tokamak reveals that the turbulent edge density
fluctuations are chaotic. Supporting evidence for this conclusion includes: the
observation of exponential power spectra (which is associated with
Lorentzian-shaped pulses in the time series), the population of the
corresponding Bandt-Pompe probability distributions (Bandt and Pompe 2002 Phys.
Rev. Lett. 88 174102), and the location of the signal on the complexity-entropy
plane (C-H plane) (Rosso et al 2007 Phys. Rev. Lett. 99, 154102 (2007)). The
classification of edge turbulence as chaotic opens the door for further work to
understand the underlying process and the impact on turbulent transport.
