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Realistic simulations of stellar surface convection with ANTARES: I. Boundary conditions and model relaxation |
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| Affiliation: | 1. Institute of Mathematics, University of Vienna, Oskar-Morgenstern-Platz 1, 1090 Vienna, Austria;2. Max-Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85748 Garching, Germany;3. BTU Cottbus, Siemens-Halske-Ring 14, 03046 Cottbus, Germany;1. Aryabhatta Research Institute of observational sciencES (ARIES), Manora Peak, Nainital 263 002, India;2. Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India;3. Kokugakuin University, Higashi, Shibuya-ku, Tokyo 150-8440, Japan;4. Kiso Observatory, School of Science, University of Tokyo, Mitake, Kiso-machi, Kiso-gun, Nagano-ken 397-0101, Japan;5. Aix Marseille Université, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille, France;6. Institute of Astronomy, National Central University, 300 Jhongda Rd, Jhongli, Taoyuan Country 32054, Taiwan;7. Department of Physics, Kumaun University, Nainital 263 002, India;1. The International Occultation Timing Association Middle East Section (IOTA/ME), Iran;2. Institute of Geophysics, University of Tehran, Tehran, Iran |
| Abstract: | We have implemented open boundary conditions into the ANTARES code to increase the realism of our simulations of stellar surface convection. Even though we greatly benefit from the high accuracy of our fifth order numerical scheme (WENO5) the broader stencils needed for the numerical scheme complicate the implementation of boundary conditions. We show that the effective temperature of a numerical simulation cannot be changed by corrections at the lower boundary since the thermal stratification does only change on the Kelvin–Helmholtz time scale. Except for very shallow models this time scale cannot be covered by multidimensional simulations due to the enormous computational requirements. We demonstrate to what extent numerical simulations of stellar surface convection are sensitive to the initial conditions and the boundary conditions. An ill-conceived choice of parameters for the boundary conditions can have a severe impact. Numerical simulations of stellar surface convection will only be (physically) meaningful and realistic if the initial model, the extent and position of the simulation box and the parameters from the boundary conditions are chosen adequately. |
| Keywords: | Hydrodynamics – methods Numerical – stars – Sun Granulation – convection |
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