Search for low-dimensional chaos in a reversed field pinch plasma

An analysis of experimental data from the reversed field experiment (RFX) reversed field pinch machine [L. Fellin, P. Kusstatscher, and G. Rostagni, Fusion Eng. Des. 25, 315 (1995)] is carried out to investigate the possible existence of deterministic chaos in the edge plasma region. The mathematical tools used include Lyapunov exponents, Kaplan-Yorke dimension, minimum embedding dimension estimates and nonlinear forecasting. The whole analysis agrees in ruling out the possibility of low-dimensional chaos: The dimension of the underlying dynamical system is estimated to be >10. From a critical rereading of the literature it emerges that the findings of this work are likely to be common to all reversed field pinches.