Simulation study of the self-reversal process in the reversed-field pinch based on a non-linearly driven reconnection model

The self-reversal process in the reversed-field pinch is studied in detail by means of a resistive magnetohydrodynamic simulation. It is confirmed that self-reversal can be caused by non-linearly driven reconnection resulting from the m=1 global kink instability, as was previously proposed by the authors. The dependence of the degree of field reversal on the pinch parameter theta and on the instability mode (resonant and non-resonant) is examined. The results are consistent with theoretical predictions. Taylor's conjecture that the total helicity is a better conserved quantity than the total magnetic energy during the relaxation process is numerically confirmed. It is found that this conjecture can be consistently explained by the non-linearly driven reconnection model. It is also found that the single helicity relaxation process has a definite energy offset from Taylor's minimum energy state. Hence, a totally relaxed state cannot be achieved through the single helicity relaxation process. Finally, the dependence of the reversal process on the resistivity is examined. (author)