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This study investigates how tidal forces dissipate energy in convective stellar interiors when tidal frequencies are much higher than the natural convection timescales. Using novel three-layered convective box simulations with periodic forcing, researchers found that tidal dissipation efficiency scales more weakly with tidal frequency than previous shear-flow models suggested, and that rotation rate significantly affects energy dissipation—slow rotation enhances it while fast rotation suppresses it. The results support theoretical predictions that effective turbulent viscosity depends only weakly on tidal frequency, though simulations were limited to tidal frequencies less than ten times the convective frequency.
Why it matters
These findings improve our understanding of how close binary star systems and star-planet systems evolve over time, as tidal interactions control the transfer of energy between orbital motion and internal stellar flows. Better models of tidal dissipation are essential for predicting the long-term stability and orbital evolution of exoplanetary systems and close stellar binaries.
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arXiv:2607.14637v2 Announce Type: replace-cross
Abstract: For close binaries and star-planet systems, tidal interactions mediate the energy transfer between the orbital motion and the internal flows of the bodies involved, thus playing a central role in their evolution. For equilibrium tides, the associated energy transfer is commonly modeled through an effective viscosity acting on the tidal flow. However, the scaling of viscous dissipation efficiency with tidal frequency $omega_text{T}$ remains debated, particularly when $omega_text{T}$ greatly exceeds the convective eddy turnover frequency $omega_text{c}$. Previous numerical studies have addressed this issue by subjecting a turbulent convective flow to an oscillating background shear mimicking equilibrium tides. In this work, we adopt a novel three-layered convective box — designed to represent a stellar convection zone sandwiched between two stable layers — driven by an external periodic forcing. We quantify tidal dissipation efficiency by the forcing power on the flow in steady state. Our results yield a shallower scaling of tidal power per unit mass with $omega_text{T}$ than reported in earlier shear-flow simulations. This scaling is consistent with the prediction by cite{Terquem2021}, suggesting that the effective turbulent viscosity depends only weakly on $omega_text{T}$, although our simulations are restricted to $omega_text{T}lesssim 10omega_text{c}$. Moreover, we find no evidence of inverse energy transfer (or “negative viscosity”), a phenomenon observed in some prior shear-flow simulations. We further investigate the influence of rotation within the same local framework. Slow rotation ($Omegalesssim omega_text{T}$) tends to enhance the tidal power, whereas fast rotation ($Omegagtrsimomega_text{T}$) significantly suppresses it. We discuss the limitations of our approach and the broader implications of our findings.
Source: Efficiency of Tidal Dissipation in Convective Flow Under Rapid Tidal Forcing