Dynamics of the overshoot layers and boundary conditions in helioseismology

The variation of both the horizontal and the vertical small scale rms velocity with height in the photosphere shows a minimum in photospheric layers about 150-200 km above the continuum. In the context of the non-equilibrum thermodynamics we suppose that the small scale rms velocity variation reflects the variation of the entropy production in these layers. We propose that the upper boundary of theoretical helioseismology models should be placed at that height where the entropy production shows its minimum