Topological analysis of a perturbed MHD equilibrium using magnetic field-line invariants

A procedure has previously been developed for the iterative construction of invariants associated with magnetic field-line Hamiltonians that consist of an axisymmetric zeroth-order term plus a non-axisymmetric perturbation. Approximate field-line invariants obtained with this procedure are used to examine the topological properties of magnetic field lines in a parabolic-current MHD equilibrium that was slightly perturbed from axisymmetry in the limit of a periodic cylindrical con✓