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

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

Corresponding author: R. Samadi, reza.samadi@obspm.fr

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, , 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 ν-dependency of  inferred from the 3D simuation in the frequency range where the acoustic energy injected into the solar p modes is important ( mHz). The ν-dependency of  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  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.