A self-consistent theory of collective alpha particle losses induced by Alfvénic turbulence

The nonlinear dynamics of kinetic Alfvén waves, resonantly excited by energetic ions/alpha particles, is investigated. It is shown that α particles govern both linear instability and nonlinear saturation dynamics, while the background magnetohydrodynamic turbulence results only in a nonlinear real frequency shift. The most efficient saturation mechanism is found to be self-induced profile modification. Expressions for the fluctuation amplitudes and the α-particle radial flux are self-consistently derived. The work represents the first self-consistent, analytical, turbulent treatment of collective α-particle losses by Alfvénic fluctuations.