Ion shielding effects on the resonant boundary layer response to magnetic perturbations

Fusion plasmas are highly sensitive to external magnetic perturbations which result in complex responses near a region known as the resonant layer. Past analytic descriptions of this phenomena used boundary layer theory in a simplified system assuming low plasma beta to predict the onset of instabilities. Here, we present a novel extension of the analytic theory utilizing nested boundary layers to capture the physics of ion parallel flow at the plasma resonant layer. This new prediction supports previous numerical results and suggests ion shielding against magnetic disruptions in parameter regimes relevant to future device operation.