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arXiv 1612.05071astro-ph.SRastro-ph.EP
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低质量恒星不同旋转对流包层中惯性波的潮汐耗散

Tidal dissipation by inertial waves in differentially rotating convective envelopes of low-mass stars

Mathieu Guenel, Stéphane Mathis, Clément Baruteau, Michel Rieutord

摘要:

在恒星-行星系统或双星系统中,潮汐相互作用会在恒星的对流区激发惯性波(惯性波的回复力是科里奥利力)。这些波的耗散在所涉及的天体的长期轨道和旋转演化中起着重要作用。如果主星作为一个固体旋转,惯性波的多普勒频移被限制在$[-2Ω, 2Ω]$范围内($Ω$是恒星的角速度),并且它们可以在整个对流区传播。然而,湍流对流可以维持与赤道加速(如在太阳)或减速,修改惯性波的频率范围和传播域,并允许非轴对称振荡的共转共振的差异旋转。在这项工作中,我们进行数值模拟潮汐激发的惯性波在差分旋转对流信封与锥形(或纬向)的旋转配置文件。我们采用的潮汐强迫包含球谐函数,对应于圆形共面轨道的情况。我们研究的粘性耗散的波作为潮汐频率的函数为各种恒星质量和微分旋转参数,以及它的依赖于湍流粘性系数。我们比较我们的结果与以前的研究假设固体旋转,并指出潜在的关键作用,共转共振的动力学演化的密切的恒星行星或二元系统。

英文摘要:

Tidal interactions in close star-planet or binary star systems may excite inertial waves (their restoring force is the Coriolis force) in the convective region of the stars. The dissipation of these waves plays a prominent role in the long-term orbital and rotational evolution of the bodies involved. If the primary star rotates as a solid body, inertial waves have a Doppler-shifted frequency restricted to the range $[-2Ω, 2Ω]$ ($Ω$ being the angular velocity of the star), and they can propagate in the entire convective region. However, turbulent convection can sustain differential rotation with an equatorial acceleration (as in the Sun) or deceleration that modifies the frequency range and propagation domain of inertial waves and allows corotation resonances for non-axisymmetric oscillations. In this work, we perform numerical simulations of tidally excited inertial waves in a differentially rotating convective envelope with a conical (or latitudinal) rotation profile. The tidal forcing that we adopt contains spherical harmonics that correspond to the case of a circular and coplanar orbit. We study the viscous dissipation of the waves as a function of tidal frequency for various stellar masses and differential rotation parameters, as well as its dependence on the turbulent viscosity coefficient. We compare our results with previous studies assuming solid-body rotation and point out the potential key role of corotation resonances in the dynamical evolution of close-in star-planet or binary systems.

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