Excitation of stellar p-modes by turbulent convection: II. The Sun

Abstract

Acoustic power and oscillation amplitudes of radial oscillations computed for a solar model are compared with solar seismic observations. The oscillations are assumed to be stochastically excited by turbulence. The numerical computations are based upon a theoretical formulation of the power going into solar-like oscillation modes, as proposed by Samadi & Goupil (2001) in a companion paper. This formulation allows us to investigate several assumptions concerning properties of the stellar turbulence. We find that the entropy source plays a dominant role in the stochastic excitation compared with the Reynold stress source, in agreement with Goldreich et al. (1994). We consider several turbulent kinetic energy spectra suggested by different observations of the solar granulation. Differences between turbulent spectra manifest in large differences in the computed oscillation powers at high oscillation frequency. Two free parameters which are introduced in the description of the turbulence enter the expression for the acoustic power. These parameters are adjusted in order to fit to the solar observations of the surface velocity oscillations. The best fit is obtained with the kinetic energy spectrum deduced from the observations of the solar granulation by Nesis et al. (1993); the corresponding adjusted parameters are found to be compatible with the theoretical upper limit which can be set on these parameters. The adopted theoretical approach improves the agreement between solar seismic observations and numerical results.