Institute of Astronomy and Astrophysics
at the Christian-Albrechts-University of Kiel

Bernd Freytag
Institut für Astronomie und Astrophysik
Universität Kiel, 24098 Kiel, Germany
Phone: +49-431-880-4103, Fax: +49-431-880-4100
Email: supas024@astrophysik.uni-kiel.de

Bernd Freytag:
Problems in Modeling Photospheric Convective Overshooting

In: ``Model Atmospheres and Spectrum Synthesis'', workshop held at Vienna, July 1995, ASP Conference Series, eds. S.J. Adelman, F. Kupka, W. W. Weiss, Volume 108, 93-98


In the art of computing stellar atmospheres and spectra the modeling of the hydrodynamical part has not kept pace with the improvements in the radiative aspects. For about 40 years convection is modelled by local mixing-length theory, assuming that convective energy flux is confined to unstable regions. But solar observations and common sense indicate that there are convective effects even outside. Detailed 2D radiation hydrodynamics simulations of the surface convection zone of the Sun and other stars show that internal, mechanical, and kinetic energy fluxes all contribute to the photospheric total convective flux, but with different signs and height dependences. They almost cancel each other in optically thin layers. Nevertheless, overshooting convective fluxes extend well into the stable photosphere up to the chromosphere and affect the temperature stratification.

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