Gyroaverage effects on nontwist Hamiltonians: separatrix reconnection and chaos suppression (Q426134)

The paper addresses an effective dynamical system governing the transport of particles in magnetized plasmas. The system is derived beyond the usual guiding-center approximation, taking into account corrections (perturbations) induced by a finite size of the Larmor radius. The accordingly perturbed system pertains to the ``nontwist'' type, which admits zero values of the derivative of the unperturbed frequency with respect to the underlying action variable. It is demonstrated that the system gives rise to a complex pattern of heteroclinic and homoclinic reconnections. The increase of the Larmor radius tends to suppress the dynamical chaos in the system.