CHARACTERISTIC PARAMETERS OF THE MAGNETIC-FIELD DUE TO THE DYNAMIC ERGODIC DIVERTOR

Resonant perturbations of sufficient amplitude impose an ergodic struc ture on the field line trajectories. In the standard theory, these fea tures are related to the amplitude of the resonant Fourier components of the B-r-field. The characteristic parameters of an ergodized field are the width of magnetic islands, the Chirikov parameter (amount of o verlapping of islands) and the coherence length (Kolmogorov length). T he perturbation current amplitude allows for Chirikov parameters of up to 1.6 for the pure 12/4 excitation mode. The Chirikov value is very sensitive to a possible mixing of 12/4 and 6/2 modes and can considera bly be enhanced. (C) 1997 Elsevier Science S.A.