- Duarte, VN;
- Berk, HL;
- Gorelenkov, NN;
- Heidbrink, WW;
- Kramer, GJ;
- Nazikian, R;
- Pace, DC;
- Podestà, M;
- Tobias, BJ;
- Van Zeeland, MA
A general criterion is proposed and found to successfully predict the emergence of chirping oscillations of unstable Alfvénic eigenmodes in tokamak plasma experiments. The model includes realistic eigenfunction structure, detailed phase-space dependences of the instability drive, stochastic scattering and the Coulomb drag. The stochastic scattering combines the effects of collisional pitch angle scattering and micro-turbulence spatial diffusion. The latter mechanism is essential to accurately identify the transition between the fixed-frequency mode behavior and rapid chirping in tokamaks and to resolve the disparity with respect to chirping observation in spherical and conventional tokamaks.