ANGULAR-MOMENTUM TRANSPORT BY INTERNAL WAVES IN THE SOLAR INTERIOR

The internal gravity waves of low frequency which are emitted at the b ase of the solar convection zone are able to extract angular momentum from the radiative interior. We evaluate this transport with some simp lifying assumptions: we ignore the Coriolis force, approximate the spe ctrum of turbulent convection by the Kolmogorov law, and couple this t urbulence to the internal waves through their pressure fluctuations, f ollowing Press (1981) and Garcia Lopez & Spruit (1991). The local freq uency of an internal wave varies with depth in a differentially rotati ng star, and it can vanish at some location, thus leading to enhanced damping (Goldreich & Nicholson 1989). It is this dissipation mechanism only that we take into account in the exchange of momentum between wa ves and stellar rotation. The flux of angular momentum is then an impl icit function of depth, involving the local rotation rate and an integ ral representing the cumulative effect of radiative dissipation. We fi nd that the efficiency of this transport process is rather high: it op erates on a timescale of 10(7) years, and is probably responsible for the flat rotation profile which has been detected through helioseismol ogy.