Contributions of fluctuation-driven Poynting flux to the energy transport in a self-organized reversed-field pinch plasma

Fluctuation measurements reveal the outward electromagnetic energy flux needed to drive the dynamo EMF supporting magnetic self-organization in a reversed-field pinch plasma. The radial Poynting flux due to tearing mode fluctuations is measured with an insertable probe during magnetic relaxation. This flux corresponds to transient power levels much larger than the input power. A simple Poynting's theorem model for an incompressible, resistive MHD plasma with resistive boundary is developed, predicting that the fluctuation-induced Poynting flux out of the plasma corresponds approximately to the power lost from the equilibrium magnetic field due to the dynamo EMF. In RFP experiments on the MST device, probe measurements of this flux are roughly as predicted by the model upon substitution of time-resolved equilibrium measurement data. Nonlinear MHD simulations using the NIMROD code are planned to examine this transport process.