Turbulent time correlations and generation of acoustic waves by stellar or solar turbulent convection

This paper considers the question of whether Eulerian or Lagrangian time correlations should be used to evaluate sound radiation by turbulent convection. Whereas previous analyses have either explicitly or implicitly used Lagrangian correlations, this paper argues in favor of Eulerian correlations. The physics of turbulent time correlations is briefly reviewed, and the implications of using Eulerian instead of Lagrangian correlations in sound-radiation calculations are discussed. The assumption made about time correlations alters the frequency distribution of the radiated sound; assuming Eulerian time correlations results in a more shallow acoustic power spectrum and consequently greater relative weighting of higher frequencies. The consequences of assuming Bolgiano scaling of buoyancy-generated turbulence are also discussed.