Transport description of the rise time of sawtooth oscillations in reversed-field pinches

High-Θ (Θ≡Bϑ(a)/〈Bφ〉) toroidal reversed-field pinch discharges in the ZT-40M device are characterized by soft x-ray sawtooth oscillations. It is demonstrated that a one-dimensional transport description is sufficient to model the rise time of sawtooth oscillations, provided the resistivity profile has significant gradients. This result suggests that the toroidal magnetic flux generation (dynamo) observed in the reversed-field pinch (RFP) may be restricted to the m=1 tearing events associated with the sawtooth crash (decrease in the soft x-ray flux).