TOPOLOGICAL ANALYSIS OF A PERTURBED MHD EQUILIBRIUM USING MAGNETIC FIELD-LINE INVARIANTS

A procedure has previously been developed for the iterative constructi on of invariants associated with magnetic field-line Hamiltonians that consist of an ax isymmetric zeroth-order term plus a non-axisymmetric perturbation. Approximate field-line invariants obtained with this pr ocedure are used to examine the topological properties of magnetic fie ld lines in a parabolic-current MHD equilibrium that was slightly pert urbed from axisymmetry in the limit of a periodic cylindrical configur ation. Excellent agreement between Poincare maps and the level curves of the fir st-order invariant is found for small perturbations. A mean s of circumventing the 'small-divisor problem' in some cases is identi fied and implemented with outstanding results. These results indicate that this perturbation method can have valuable consequences for futur e investigations of magnetic field-line topology.