Reconstruction of VMEC 3D Equilibrium Fields
VMEC imposes perfect magnetic surfaces - physically this implies perfectly conducting plasma and singular current sheets in 3D
Given VMEC Bj and Jj, one finds F and from
Physically singular currents are not rigorously retained in VMEC (weak solution) output. The absence of the cancellation singular currents allows island opening and stochasticity. Field line tracing gives a quantitative assessment. (Boozer, 99)