A mean field description of reversed field pinch: equilibrium, dynamo, plasma heating and confinement

Three simple physics constraints are applied to describe the reversed field pinch (RFP) in a mean field sense. These constraints are: (a) a steady state equilibrium, (b) a negative radial pressure gradient, and (c) a net volumetric source of mean field magnetic energy that is always locally negative. Using these constraints, realistic RFP equilibria are calculated, plasma heating profiles are determined, and the role of the dynamo in rearranging profiles can be described by a mean field one dimensional picture. The RFP exists in a near minimum energy state characterized by a mu profile (where ? identical to ? 0aJ.B/B2) that decreases to a small value at the plasma edge. The resulting RFP confinement picture has three regions: a poorly confined plasma core characterized by parallel (radial) transport and flux surfaces destroyed by m=1 tearing mode activity associated with dynamo relaxation, a medium confined edge limited by ideal pressure gradient driven modes, and a good confinement region located near the reversal layer. This good confinement region determines the global confinement characteristics of the RFP, and, if limited by resistive interchange modes, is consistent with the Conner-Taylor scaling that has provided a good fit to international RFP results