Oscillations of the solar radial pmodes.
Abstract
We have calculated the radial nonadiabatic pmode oscillations of the solar models. Based on a statistical theory of nonlocal convection, both the thermodynamic and kinetic couplings between convection and oscillations are finely treated. The turbulent pressure, turbulent viscosity, turbulent thermal flux and turbulent kinetic flux are all selfconsistently included in the equations. The departure from the radiative equilibrium is treated exactly in the Eddington's approximation. The radiation field and gas are separately considered throughout, and they are coupled by the gaseous absorption and radiation. The generalized Mihalas' radiative hydrodynamic equations, and the dynamic equations of the auto and the crosscorrelations of the turbulent temperature and velocity fluctuations together form a set of selfconsistent complete equations. It is shown by numeric calculation that all pmodes with n=013 are pulsational unstable when the coupling between convection and oscillations was neglected, and the pmodes with n=632 are unstable while that coupling was included. The thermodynamic coupling between convection and oscillations is the chief excitation mechanism, which occurs predominantly in the superadiabatic convection region. Turbulent pressure is always a destabilization factor. With increasing frequency, the turbulent viscosity increases more rapidly than the turbulent pressure does and becomes a dominate damping factor. The nonadiabatic effects on oscillation frequencies are not negligible, they caused a change of the frequencies up to several microhertzs. The departure from the radiative equilibrium has significant effects on stability of the solar pmodes. But these effects usually only alter the value of the stability coefficient but not its sign. The influence of the nonadiabatic effects and nonradiative equilibrium increases with increasing frequency of pmode oscillations.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 March 1997
 Bibcode:
 1997A&A...319..981C
 Keywords:

 CONVECTION;
 SUN: OSCILLATIONS;
 INTERIOR