Stellar mixing

V. Overshooting^⋆

¹ NASA, Goddard Institute for Space Studies, New York, NY 10025, USA
² Department of Applied Physics and Applied Mathematics, Columbia University, New York, NY 10027, USA
e-mail: vmc13@columbia.edu

Received: 17 March 2010
Accepted: 10 October 2010

Abstract

Helio-seismological data suggest an overshooting (OV) extent of 0.07 H_p (H_p is the pressure scale height), while theoretical predictions from both models and numerical simulations yield values that are an order of magnitude higher. The reason identified by the authors of numerical simulations is the limited range of physical parameters allowed by the numerical simulations compared to the true solar values; specifically, the simulations are still too viscous. In the case of theoretical models, we discuss limitations that at present cannot be solved. For these reasons, we propose and work out a different methodology, which has in principle the following advantages. First, there is no longer a need to model the flux of turbulent kinetic energy, which has been a stumbling block for many years and whose modeling has introduced uncertainties that are difficult to control. Second, we account for processes not included before: shear (differential rotation), meridional currents, gravitational energy, stable-unstable stratification, and double diffusion.