Prediction of Nonlinear Evolution Character of
Energetic-Particle-Driven Instabilities
Authors: V.N. Duarte, N. Gorelenkov, G. J. Kramer,
R. Nazikian, M. Podestà , and B. J. Tobias
Abstract: A general criterion is proposed and found to
successfully predict the emergence of chirping oscillations of
unstable Alfvenic 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.