Volume 522, November 2010
|Number of page(s)||4|
|Published online||26 October 2010|
Letter to the Editor
Turbulent eddy-time-correlation in the solar convective zone
Institut d’Astrophysique et de Géophysique, Université de
Allée du 6 août 17,
2 LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195 Meudon Cedex, France
3 Institut d’Astrophysique Spatiale, CNRS-Université Paris XI UMR 8617, 91405 Orsay Cedex, France
4 Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
5 Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
Accepted: 6 October 2010
Theoretical modeling of the driving processes of solar-like oscillations is a powerful way of understanding the properties of the convective zones of solar-type stars. In this framework, the description of the temporal correlation between turbulent eddies is an essential ingredient to model mode amplitudes. However, there is a debate between a Gaussian or Lorentzian description of the eddy-time correlation function (Samadi et al. 2003b, A&A, 403, 303; Chaplin et al. 2005, MNRAS, 360, 859). Indeed, a Gaussian description reproduces the low-frequency shape of the mode amplitude for the Sun, but is unsatisfactory from a theoretical point of view (Houdek 2010, Ap&SS, 328, 237) and leads to other disagreements with observations (Samadi et al. 2007, A&A, 463, 297). These are solved by using a Lorentzian description, but there the low-frequency shape of the solar observations is not correctly reproduced. We reconcile the two descriptions by adopting the sweeping approximation, which consists in assuming that the eddy-time-correlation function is dominated by the advection of eddies, in the inertial range, by energy-bearing eddies. Using a Lorentzian function together with a cut-off frequency derived from the sweeping assumption allows us to reproduce the low-frequency shape of the observations. This result also constitutes a validation of the sweeping assumption for highly turbulent flows as in the solar case.
Key words: convection / turbulence / Sun: oscillations
© ESO, 2010
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