Recurrence in plasma edge turbulence

Abstract

Common statistics of turbulent electrostatic fluctuations observed at the plasma edge and scrape-off layer are analyzed in three tokamak devices that have different configurations. The statistics of experimental data collected using fixed sampling time is the same than the statistics of the time for which the oscillation return to a specified reference interval of values. This observation, in addition to the finding of power-scaling laws for some average quantities with respect to either the sampling time or the size of the reference interval, suggests that turbulence on tokamaks have recurrent characteristics, typical of a recurrent chaotic low-dimensional system. Furthermore, the first Poincaré recurrence time and other dynamical tools are used to simulate the mentioned fluctuation statistical properties.