Tidal Dissipation in Rotating Solar‐Type Stars

We calculate the excitation and dissipation of low-frequency tidaloscillations in uniformly rotating solar-type stars. For tidal frequenciessmaller than twice the spin frequency, inertial waves are excited in theconvective envelope and are dissipated by turbulent viscosity. Enhanceddissipation occurs over the entire frequency range rather than in a series ofvery narrow resonant peaks, and is relatively insensitive to the effectiveviscosity. Hough waves are excited at the base of the convective zone andpropagate into the radiative interior. We calculate the associated dissipationrate under the assumption that they do not reflect coherently from the centerof the star. Tidal dissipation in a model based on the present Sun issignificantly enhanced through the inclusion of the Coriolis force but maystill fall short of that required to explain the circularization of closebinary stars. However, the dependence of the results on the spin frequency,tidal frequency, and stellar model indicate that a more detailed evolutionarystudy including inertial and Hough waves is required. We also discuss the caseof higher tidal frequencies appropriate to stars with very close planetarycompanions. The survival of even the closest hot Jupiters can be plausiblyexplained provided that the Hough waves they generate are not damped at thecenter of the star. We argue that this is the case because the tide excited bya hot Jupiter in the present Sun would marginally fail to achieve nonlinearity.As conditions at the center of the star evolve, nonlinearity may set in at acritical age, resulting in a relatively rapid inspiral of the hot Jupiter.Comment: 12 pages, 7 figures, to be published in Astrophys.