Analysis of tokamak data using a novel Hilbert transform based technique

Abstract

A novel data analysis technique based on the “empirical mode decomposition” and Hilbert transform is applied to the analysis of edge fluctuation data and Mirnov coil data from the ADITYA tokamak [S. B. Bhatt et al., Ind. J. Pure Appl. Phys. 27, 710 (1989)]. It is shown that the edge fluctuations can be well represented by a finite number of about 10 discrete modes. Their instantaneous energies show intermittent bursts and the high frequency modes are nonstationary. The technique is further developed to study three-mode interactions and employed to show that triplet interactions are statistically significant among high frequency modes of the fluctuation data. A general critique of the method is presented and its utility for the analysis of nonlinear phenomena in complex systems like plasma turbulence is highlighted.