Effects of the Shafranov shift on the ballooning mode in negative shear

In negative shear tokamak discharges, an excessively large Shafranov shift (deltaʹ) destabilizes the magnetohydrodynamic ballooning mode. A kinetic model, local to a flux surface and which employs the ballooning-mode representation of the gyrokinetic equations, also predicts the existence of the instability as does two-fluid theory.