Effect of reconnection of magnetic field lines and electron thermal conduction on the plasma pressure gradient in a sawtooth oscillation

In a sawtooth oscillation, the resistive reconnection and the internal disruption are two distinct and sequential events. At the beginning of the reconnection of magnetic field lines around an m=1 magnetic island, the mixing of the electron temperatures associated with the reconnection results in an increasing island width and a steep pressure gradient in the boundary layer adjacent to the reconnecting surface, leading to the destabilization of ideal MHD modes. The thickness of the boundary layer is determined by the ratio of electron cross-field thermal diffusivity and the speed of reconnection. This narrow boundary layer and the short onset time of a sawtooth crash can be supported by 'fine-grained' transport processes which drive the electron energy loss in a tokamak plasma. (author). Letter-to-the-editor. 11 refs