Dynamics of the Sawtooth Collapse in Tokamak Plasmas

Fast reconnection such as driven by electron inertia qualitatively changes the Kadomtsev picture of the sawtooth collapse in tokamak discharges. The collapse occurs in two steps, a fast Kadomtsev-type reconnection followed by a rapid reformation of a $q_0<1\mathrm{}$ configuration. The latter is driven by the strong flows generated during the Kadomtsev phase. The theory provides a natural explanation of the main experimental observations including the snake phenomena.