  Internal gravity waves are excited at the interface of convection and
radiation zones of a solar-type star by the tidal forcing of a short-period
planet. The fate of these waves as they approach the centre of the star depends
on their amplitude. We discuss the results of numerical simulations of these
waves approaching the centre of a star, and the resulting evolution of the spin
of the central regions of the star, and the orbit of the planet. If the waves
break, we find efficient tidal dissipation, which is not present if the waves
perfectly reflect from the centre. This highlights an important amplitude
dependence of the (stellar) tidal quality factor Q', which has implications for
the survival of planets on short-period orbits around solar-type stars, with
radiative cores.
