Sawtooth Stabilization and Onset of Alfvenic Instabilities

Tokamak sawtooth instabilities can be stabilized by high energy particles as a consequence of conservation of the third adiabatic invariant.\footnote{D.J. Campbell {\it et al.}, Phys. Rev. Lett. {\bf 60}, 2148 (1988); F.Porcelli, Plasma Phys. Controlled Fusion {\bf 33}, 1601 (1991).} On the other hand, termination of the stabilized period is reported due to the onset of Alfvenic instabilities (and thus the absence of the stabilizing mechanism).\footnote{S.Bernabei {\it et al.}, Phys. Rev. Lett. {\bf 84}, 1212 (2000); steeping of the pressure gradient (of high energy particle components) triggers Alfvenic instabilities.} In this work, employing a kinetic-fluid model,\footnote{C.Z.Cheng and J.R.Johnson, J.Geophys. Res. {\bf 104}, 413 (1999).} the interaction of m=1 resistive kink mode and high energy particles is investigated. The onset of Alfvenic instabilities is examined as a function of the inversion radius location.