Compatibility of the turbulent dynamo concept with reversed field pinches

The sustainment phase of reversed field pinches (RFP’s) is investigated with the concept of the turbulent dynamo. In the case of a finite toroidal voltage, the familiar alpha–beta dynamo, which is equivalent to Taylor’s and modified Bessel function models, cannot satisfy the condition of vanishing currents at the plasma edge. The importance of another alpha term is stressed, and the deep reversal resulting from a large toroidal voltage, the enhanced dynamo effect in ramped discharges, and the F-Θ pumping are discussed in light of the characteristics of the edge region that have a great influence on the global structure of the RFP.