Vibrational stability of G plus modes towards non-radial oscillations for solar models

The vibrational stability of solar models towards g plus modes has been studied from the Zero Age Main Sequence (ZAMS) up to the age of 5 billion yr. The nuclear energy contribution to instability is calculated with the effective sensitivity of the reactions to change of temperature. The perturbation of convective terms is taken from an extension for nonradial oscillations of Unno's theory. The ZAMS model and the present sun are stable. However, for intermediate ages, models are unstable with respect to the lowest modes due to the effects of nuclear reactions. If, moreover, the mechanical effects of convection are taken into account, all models are unstable. However their theory is uncertain enough to require caution.