Transport barrier inside the reversal surface in the chaotic regime of the reversed-field pinch

Magnetic field lines and the corresponding particle orbits are computed for a typical chaotic magnetic field provided by a magnetohydrodynamics numerical simulation of the reversed-field pinch. The m=1 modes are phase locked and produce a toroidally localized bulging of the plasma which increases particle transport. The m=0 and m=1 modes produce magnetic chaos implying poor confinement. However, they also allow for the formation of magnetic islands which induce transport barriers inside the reversal surface.