Efficiency of tidal dissipation in slowly rotating fully convective stars or planets
| Autor: | Adrian J. Barker, Jérémie Vidal |
|---|---|
| Přispěvatelé: | School of Mathematics - University of Leeds, University of Leeds, School of Mathematics [Leeds] |
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Convection
[PHYS.PHYS.PHYS-FLU-DYN]Physics [physics]/Physics [physics]/Fluid Dynamics [physics.flu-dyn] Convective heat transfer [SDU.ASTR.EP]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Earth and Planetary Astrophysics [astro-ph.EP] FOS: Physical sciences 01 natural sciences Power law Physics::Fluid Dynamics Viscosity 0103 physical sciences 010306 general physics 010303 astronomy & astrophysics Solar and Stellar Astrophysics (astro-ph.SR) Physics Earth and Planetary Astrophysics (astro-ph.EP) Turbulence [SDU.ASTR.SR]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Solar and Stellar Astrophysics [astro-ph.SR] Fluid Dynamics (physics.flu-dyn) Astronomy and Astrophysics Physics - Fluid Dynamics Dissipation Computational physics Eddy Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science Cascade Astrophysics - Earth and Planetary Astrophysics |
| Zdroj: | Monthly Notices of the Royal Astronomical Society Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P-Oxford Open Option A, In press, 000, pp.1-14 Monthly Notices of the Royal Astronomical Society, Oxford University Press (OUP): Policy P-Oxford Open Option A, 2020, 497 (4), pp.4472-4485. ⟨10.1093/mnras/staa2239⟩ |
| ISSN: | 0035-8711 1365-2966 |
| Popis: | Turbulent convection is thought to act as an effective viscosity in damping equilibrium tidal flows, driving spin and orbital evolution in close convective binary systems. Compared to mixing-length predictions, this viscosity ought to be reduced when the tidal frequency $|\omega_t|$ exceeds the turnover frequency $\omega_{c\nu}$ of the dominant convective eddies, but the efficiency of this reduction has been disputed. We reexamine this long-standing controversy using direct numerical simulations of an idealized global model. We simulate thermal convection in a full sphere, and externally forced by the equilibrium tidal flow, to measure the effective viscosity $\nu_E$ acting on the tidal flow when $|\omega_t|/\omega_{c\nu} \gtrsim 1$. We demonstrate that the frequency reduction of $\nu_E$ is correlated with the frequency spectrum of the (unperturbed) convection. For intermediate frequencies below those in the turbulent cascade ($|\omega_t|/\omega_{c\nu} \sim 1-5$), the frequency spectrum displays an anomalous $1/\omega^\alpha$ power law that is responsible for the frequency-reduction $\nu_E \propto 1/|\omega_t|^{\alpha}$, where $\alpha < 1$ depends on the model parameters. We then get $|\nu_E| \propto 1/|\omega_t|^{\delta}$ with $\delta > 1$ for higher frequencies, and $\delta=2$ is obtained for a Kolmogorov turbulent cascade. A generic $|\nu_E| \propto 1/|\omega_t|^{2}$ suppression is next found for higher frequencies within the dissipation range of the convection (but with negative values). Our results indicate that a better knowledge of the frequency spectrum of convection is necessary to accurately predict the efficiency of tidal dissipation in stars and planets resulting from this mechanism. Comment: 14 pages, 17 figures, 1 table, published 6 August 2020 in MNRAS |
| Databáze: | OpenAIRE |
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