EDP Sciences
Free access
Issue
A&A
Volume 404, Number 3, June IV 2003
Page(s) 1129 - 1137
Section Diffuse matter in space
DOI http://dx.doi.org/10.1051/0004-6361:20030504


A&A 404, 1129-1137 (2003)
DOI: 10.1051/0004-6361:20030504

Numerical 3D constraints on convective eddy time-correlations: Consequences for stochastic excitation of solar p modes

R. Samadi1, 2, Å. Nordlund3, R. F. Stein4, M. J. Goupil2 and I. Roxburgh1, 2

1  Astronomy Unit, Queen Mary, University of London, London E14NS, UK
2  Observatoire de Paris, LESIA, CNRS UMR 8109, 92195 Meudon, France
3  Niels Bohr Institute for Astronomy, Physics, and Geophysics, Copenhagen, Denmark
4  Department of Physics and Astronomy, Michigan State University, Lansing, USA

(Received 9 December 2002 / Accepted 30 March 2003 )

Abstract
A 3D simulation of the upper part of the solar convective zone is used to obtain information on the frequency component, $\chi_k$, of the correlation product of the turbulent velocity field. This component plays an important role in the stochastic excitation of acoustic oscillations. A time analysis of the solar simulation shows that a Gaussian function does not correctly reproduce the $\nu$-dependency of  $\chi_k$ inferred from the 3D simuation in the frequency range where the acoustic energy injected into the solar p modes is important ( $\nu \simeq 2 {-} 4$ mHz). The $\nu$-dependency of  $\chi_k$ is fitted with different analytical functions which can then conveniently be used to compute the acoustic energy supply rate P injected into the solar radial oscillations. With constraints from a 3D simulation, adjustment of free parameters to solar data is no longer necessary and is not performed here. The result is compared with solar seismic data. Computed values of  P obtained with the analytical function which fits best  $\chi_k$ are found ~2.7 times larger than those obtained with the Gaussian model and reproduce better the solar seismic observations. This non-Gaussian description also leads to a Reynolds stress contribution of the same order as the one arising from the advection of the turbulent fluctuations of entropy by the turbulent motions. Some discrepancy between observed and computed  P values still exist at high frequency and possible causes for this discrepancy are discussed.


Key words: convection -- turbulence -- stars: oscillations -- Sun: oscillations

Offprint request: R. Samadi, reza.samadi@obspm.fr




© ESO 2003