Electrostatic turbulence intermittency and MHD relaxation phenomena in a RFP plasma

The basic statistical features of the electrostatic fluctuations in the edge plasma of the RFX reversed field pinch fusion device and their relationship with magnetic relaxation events are reported. The analysis of time series of floating potential measurements obtained at low plasma current (< 400 kA) has shown a clear relation between low-frequency (f < 5 kHz) electrostatic fluctuations and reversal parameter F fluctuations related to relaxation events. The electrostatic turbulence measurements have been investigated through the wavelet decomposition technique, and intermittent structures have been identified. These structures are found to occur mainly during relaxation events. The probability distribution function of waiting times between intermittent structures shows a power law trend, which is a clear evidence of memory-characterized phenomena. (orig.)