Intermittency in plasma turbulence

Intermittency in fluid turbulence can be evidentiated through the analysis of Probability Distribution Functions (PDF) for velocity fluctuations, which display a strong non-Gaussian behaviour at small scales. In this paper, we investigate the occurrence of intermittency in plasma turbulence by studying the departure from the Gaussian distribution of PDF for both velocity and magnetic fluctuations. We use data coming from two different experiments, namely in situ satellite observations of the inner solar wind and turbulent fluctuations in a magnetically confined fusion plasma. Moreover, we investigate also time intermittency observed in a simplified shell model which mimics 3D MED equations, We found that the departure from a Gaussian distribution is the main characteristic of all cases. The scaling behaviour of PDFs are then investigated by using two different models built up in the past years, in order to capture the essence of intermittency in turbulence. (C) 2001 Elsevier Science Ltd. All rights reserved.