Stability of nonradial g+-mode pulsations in 1 M/sub sun/ models

The stability of nonradial g+ modes with low l in evolutionary solar models is examined by employing a linear nonadiabatic analysis. In order to include the effect of the interaction between pulsation and convection, we use a time-dependent convection theory which suppresses rapid spatial oscillations of thermal eigenfunctions. The analysis confirms previous results based on quasi-adiabatic analyses. That is, some low-order g+ modes are unstable in the early evolutionary stages of the models. In these cases, the effect of the convection zone in the envelope is relatively small. We find that the g2+ mode with l=1 (with a period of about 80 minutes) is unstable even in a model of age 4.5 x 109 yr. This mode is excited by both the driving mechanisms of the 3He+3He reaction in the core and the hydrogen ionization in the envelope. A larger mixing length yields stronger excitation, but the dependence is not strong