Pressure driven dynamics and global energy transport in finite beta RFP computations

Finite-beta visco-resistive non-linear MHD computations are applied to self-consistently model RFP relaxation and energy transport. Linear resistive MHD analysis of the dominant fluctuations from the quasi-steady conditions shows that these RFP equilibria are tearing unstable. RFPs have bad curvature implying that pressure has a role to play in tearing dynamics. To assess the pressure drive, linear eigenfunctions are used to compare stabilizing and destabilizing contributions to the perturbed kinetic energies. While most of the stabilizing contribution from the field-line bending force is annihilated by resistive diffusion, the parallel current term alone does not drive tearing. Pressure drive is always comparable and provides a significant destabilizing contribution for tearing modes. Fluctuation induced outward energy transport from the core of the RFP comes largely from parallel thermal conduction. Second order correlations of magnetic fluctuations and parallel heat flux however, do not result in net outward energy transport at all radii. Taking into account higher order correlations shows that third order correlations are larger and cancel the inward transport from quadratic correlations near the reversal surface.