2000BaltA...9...33V

Several analyses and qualitative arguments excluded resonant mode coupling and nonlinear driving as the main nonlinear processes responsible for the presence of the numerous cross-frequencies in the temporal spectrum of GD 358. Rather, harmonic distortion is the prime cause. We believe that the nonlinear response of the convection zone to the oscillatory perturbation is the dominant harmonic distortion mechanism. The amplitude variations recorded in the temporal spectrum of GD 358 might be accounted for by long period beating between eigenmodes and third-order cross-frequencies. This permanent process is referred to as high-order beating.