ALFVEN-ION-CYCLOTRON INSTABILITY AND ABSENCE OF SAWTEETH IN TOKAMAKS

Linear stability of the anisotropic energetic ion population, observed in recent experiments at the Joint European Torus [Phys. Rev. Lett. 60,2148 (1988)], to Alfvén-ion cyclotron wave excitations is analyzed and the saturation mechanism is discussed. In the absence of external heating the anisotropic distribution lifetime is found comparable to the observed delay time in the monster sawtooth crash after the turn-off of the heating. It is suggested that the ponderomotive force of unstable waves is responsible for this delay. Saturated wave fields are found sufficiently large to stabilize the internal kink mode. © 1990 American Institute of Physics.