Hydrodynamical stellar models including rotation, internal gravity waves, and atomic diffusion - I. Formalism and tests on Pop I dwarfs

In this paper, we develop a formalism, in order to incorporate the contribution of internal gravity waves to the transport of angular momentum and chemicals over long time-scales in stars. We show that the development of a double-peaked shear layer acts as a filter for waves, and also how the asymmetry of this filter produces momentum extraction from the core when it is rotating faster than the surface. Using only this filtered flux, it is possible to follow the contribution of internal waves over long ( evolutionary) time-scales. We then present the evolution of the internal rotation profile using this formalism for stars which are spun down via magnetic torquing. We show that waves tend to slow down the core, creating a slow front that may then propagate from the core to the surface. Further spin down of the surface leads to the formation of a new front. Finally we show how this momentum transport reduces rotational mixing in a 1.2 M-., Z = 0.02 model, leading to a surface lithium abundance in agreement with observations in the Hyades.