Spectrum and amplitudes of internal gravity waves excited by penetrative convection in solar-type stars

¹ Observatoire Midi-Pyrénées, UMR 5572, Université Paul Sabatier et CNRS, 31400 Toulouse, France e-mail: boris.dintrans@obs-mip.fr
² NORDITA, Blegdamsvej 17, 2100 Copenhagen Ø, Denmark
³ Niels Bohr Institute, Juliane Maries Vej 30, 2100 Copenhagen Ø, Denmark
⁴ Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824, USA

Received: 7 February 2005
Accepted: 5 April 2005

Abstract

The excitation of internal gravity waves by penetrative convective plumes is investigated using 2-D direct simulations of compressible convection. The wave generation is quantitatively studied from the linear response of the radiative zone to the plumes penetration, using projections onto the g-modes solutions of the associated linear eigenvalue problem for the perturbations. This allows an accurate determination of both the spectrum and amplitudes of the stochastically excited modes. Using time-frequency diagrams of the mode amplitudes, we then show that the lifetime of a mode is around twice its period and that during times of significant excitation up to 40% of the total kinetic energy may be contained into g-modes.