A resonant tidal torque is exerted at the outer boundary of the interior convection zone.
Tidal dissipation occurs through nonlinear damping.
This process is similar to that previously considered for high-mass binary stars. Gravity waves carrying angular momentum are launched outward from the resonant region. As these waves damp by nonlinear processes, an over-synchronous planet is spun down towards synchronism with the orbit. These estimates ignore effects of tidal heating, which are likely important at the spin rate of Jupiter or higher. A planet's photosphere would be spun down even more effectively than is estimated above, if its outer layers can rotate differentially.