MIXING BY INTERNAL WAVES .1. LITHIUM DEPLETION IN THE SUN

We present in this paper a new model for internal wave generation by d isturbances at the bottom of the convective region in the frame of the convective penetration model by Zahn (1991). Several morphologies are proposed for these per turbations. Fourier analysis and the results f rom Press (1981) for sinusoidal perturbation, provide us with analytic al expression for the velocity field in the stellar radiative interior . A diffusion coefficient is obtained using the definition of macrosco pic diffusion coefficient given by Schatzman (1991) following Press' s uggestion of irreversibility of the process in the radiative interior. The comparison between observations and Li depletion provided by this diffusive process in the Sun, shows that it is possible to justify wi th this process a Li depletion factor of 10(2) if we assume the distur bance described by a plume, and with a velocity of the downdraft in th e convective zone four times that one given by the mixing length theor y. Furthermore, the results are compatible with the pre-main-sequence (PMS) lithium burning.