Empirical modeling and the dependence of reversed field pinch loop voltage on edge plasma conditions

Empirical modeling of the dependence of loop voltage on edge plasma conditions in the reversed field pinch is discussed. Specific concerns are raised regarding magnetohydrodynamic‐based models that assume a large local dissipation of magnetic helicity at the plasma edge. A kinetic model is presented in which loop voltage can be affected by fast electrons carrying momentum directly to the walls or limiters, without a large edge helicity dissipation.