Sawtooth Reconnection Complete Sawtooth Reconnection Model

• sawtooth cycle:- temperature rises slowly- safety factor on axis drops below unity- (1,1) internal kink is destabilized- (1,1) magnetic island develops on q=1 surface- surfaces of equal helical magnetic flux reconnect until the island has replaced the core- as island O-point becomes new magnetic axis, the safety factor on axis becomes unity- configuration becomes stable • central temperature drop is explained by hot core being expelled and replaced by colder island Incomplete Sawtooth Reconnection • observations of sawteeth in various tokamaks contradict Kadomtsev's model- (1,1) mode survives the crash [8,3]- safety factor on axis remains below unity [9-11] • incomplete sawtooth reconnection model needs to account for:- saturation of island before reconnection is complete- mechanism for heat release • possible explanation:- mode coupling causes field lines to ergodize, starting at island X-point- ergodization enhances heat transport- flattening of temperature profiles reduces drive of instabilit