The effect of random flow on solar acoustic waves

We examine the influence of a random flow that occurs in the convection zone on frequencies of the solar acoustic oscillations. Using a perturbative method the dispersion relation is derived in the case of a random flow that is parallel to the wave propagation. This relation is subsequently solved numerically for various parameters of the random field to find the frequencies of the random acoustic waves. The numerical results reveal that these waves can be both amplified and damped by the random flow; also their frequencies can be higher and lower than the frequencies of the coherent acoustic waves. The amplification and frequency increase are more pronounced for low spherical harmonic degree l, stronger random flow, and lower spatial correlation length. These analytical findings are tested against numerical simulations for the full set of linear equations, without introducing a weak random field approximation. Numerical results reveal for the first time wave amplification and frequency decrease of the sound waves.