Nonlinear saturation of nonresonant internal instabilities in a straight spheromak

An initial value numerical solution of the time-dependent nonlinear ideal magnetohydrodynamic equations demonstrates that spheromak equilibria which are linearly unstable to nonresonant helical internal perturbations saturate at low amplitude without developing singularities. These instabilities thus represent the transition from an axisymmetric to a nonaxisymmetric equilibrium state, caused by a peaking of the current density