Effect of parallel flow on resonant layer responses in high beta plasmas

Abstract

Resonant layers in a tokamak respond to non-axisymmetric magnetic perturbations by amplifying a mode amplitude and balancing a plasma rotation through magnetic reconnection and force balance, respectively. This resonant response can be characterized by local layer parameters and especially by a single quantity in the linear regime, the so-called inner-layer $\Delta$. The computation of $\Delta$ under two-fluid drift-MHD formalism has been progressed by reducing an order of system in the phase space, where the shielding current was approximated as being only carried by electrons, as \textit{a posteriori}. In this study, we relax the approximation and compute $\Delta$ accounted for by the parallel flow that is associated with the ion shielding current. The posteriori is numerically verified by great agreement with original SLAYER developed by a previous paper [J.-K. Park, Phys. Plasmas \textbf{29}, 072506 (2022)]. Extending the resonant layer response theory to high $\beta$ plasmas, our research findings answer to two important questions, how the parallel flow influences the resonant layer response and why the parallel flow effect appears in high $\beta$ plasmas. This work is envisaged to predict the resonant layer response under high $\beta$ fusion reactor condition. Technically, the Riccati matrix transformation method is adapted to handle the numerical stiffness due to the increased order of system. The high fidelity of this numerical method makes use of further extension of the model to more higher order system to take other physical phenomena into account.