Sustained Self-Reversal in the Reversed-Field Pinch

Spontaneous reversal of the toroidal field in a reversed-field pinch as a result of low-$\beta$ (small $\frac{J_{\perp }}{J_{\parallel }}$) resisitive kink mode activity is investigated with use of a three-dimensional magnetohydrodynamics code. Helical and three-dimensional steady reversed states are obtained. In three dimensions quasisteady fluctuating states are observed above a critical value of the pinch parameter $\theta$.