Nonlinear Ion-Temperature-Gradient-Driven Instability in Low-Collisionality Plasmas

A novel theory for the self-consistent evolution of a nonlinear trapped-ion temperature-gradient-driven instability, based on the turbulent trapping of resonant ions in the electrostatic potential of the waves, is proposed. Threshold-dependent, non-steady-state turbulence (nonlinear instability) is shown to develop. The resulting anomalous thermal and particle transports act to reconfigure the equilibrium temperature and density profiles in such a way as to return the system towards marginality. Implications of the theory for present and future-generation fusion experiments are discussed.