Nonlinear reversed shear Alfvén eigenmode saturation due to spontaneous zonal current generation

Long-Term Landau-Fluid Simulation of Alfvén Eigenmode Instabilities∗)

An energetic particle Landau-fluid closure model (TAEFL) is applied to a case where both RSAE (Reversed Shear Alfvén Eigenmode) and TAE (Toroidal Alfvén Eigenmode) modes are destabilized by beam ions. The nonlinear evolution of the coupled modes are followed for about 104 Alfvén times under the simplifying assumptions that a density source is present that exactly balances the quasi-linear fast ...

Nonlinear excitations of zonal structures by toroidal Alfvén eigenmodes.

Zonal flows and, more generally, zonal structures are known to play important self-regulatory roles in the dynamics of microscopic drift-wave-type turbulences. Since toroidal Alfvén eigenmode (TAE) plays crucial roles in the Alfvén wave instabilities in burning fusion plasmas, it is, thus, important to understand and assess the possible roles of zonal flow and structures on the nonlinear dynami...

An Enhanced Nonlinear Critical Gradient for Electron Turbulent Transport due to Reversed Magnetic Shear

Laboratory observation of a nonlinear interaction between shear Alfvén waves.

An experimental investigation of nonlinear interactions between shear Alfvén waves in a laboratory plasma is presented. Two Alfvén waves, generated by a resonant cavity, are observed to beat together, driving a pseudomode at the beat frequency. The pseudomode then scatters the Alfvén waves, generating a series of sidebands. The observed interaction is very strong, with the normalized amplitude ...

Nonlinear dynamics of beta-induced Alfvén eigenmode driven by energetic particles.

Nonlinear saturation of a beta-induced Alfvén eigenmode, driven by slowing down energetic particles via transit resonance, is investigated by the nonlinear hybrid magnetohyrodynamic gyrokinetic code. Saturation is characterized by frequency chirping and symmetry breaking between co- and counter-passing particles, which can be understood as the evidence of resonance detuning. The scaling of the ...