2021/01/15 by K. Belkacem, F. Kupka, J. Philidet +1
Physics and Astronomy · #Adiabatic process #Astrophysics and Star Formation Studies #Buoyancy #Compressibility #Dissipation #Hydrostatic equilibrium #Kinetic energy #Perturbation (astronomy) #Solar and Space Plasma Dynamics #Stellar, planetary, and galactic studies #Turbulence #astro-ph.SR #physics.flu-dyn
paper · pdf · doi:10.1051/0004-6361/202040259
published as A&A 646, L5 (2021) · 7 pages, 1 figure. Accepted as a Letter in Astronomy and Astrophysic
arxiv created 2021/01/15 · openalex publication_date 2021/01/20 · openalex created_date 2021/02/01 · arxiv updated 2021/02/10 · openalex updated_date 2026/08/05
The application of the full potential of stellar seismology is made difficult by the improper modelling of the upper-most layers of solar-like stars and their influence on the modelled frequencies. Our knowledge of these so-called ‘surface effects’ has improved thanks to the use of 3D hydrodynamical simulations, however, the calculation of eigenfrequencies relies on empirical models for the description of the Lagrangian perturbation of turbulent pressure, namely: the reduced-Γ 1 model (RGM) and the gas-Γ 1 model (GGM). Starting from the fully compressible turbulence equations, we derived both the GGM and RGM models by using a closure to model the flux of turbulent kinetic energy. We find that both models originate from two terms: the source of turbulent pressure due to compression produced by the oscillations and the divergence of the flux of turbulent pressure. We also demonstrate that they are both compatible with the adiabatic approximation and, additionally, that they imply a number of questionable assumptions, mainly with respect to mode physics. Among other hypotheses, it is necessary to neglect the Lagrangian perturbation of the dissipation of turbulent kinetic energy into heat and the Lagrangian perturbation of buoyancy work.