Tidal dissipation due to the elliptical instability and turbulent viscosity in convection zones in rotating giant planets and stars
Tidal dissipation due to the elliptical instability and turbulent viscosity in convection zones in rotating giant planets and stars
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由于旋转巨行星和恒星对流区的椭圆不稳定性和湍流粘度而引起的潮汐耗散
DOI：
10.1093/mnras/stad1990
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发表时间：
2023
影响因子：
4.8
通讯作者：
De Vries N
中科院分区：
文献类型：
--
作者：
De Vries N
恒星-行星系统中的潮汐耗散可以通过多种机制发生，其中椭圆不稳定性就是其中之一。这作用于旋转流体行星和恒星中椭圆变形的平衡潮汐流，如果无量纲潮汐振幅（λ）足够大，就会在对流区域激发惯性波。我们研究了它与湍流对流的相互作用，并试图限制椭圆不稳定性和对流对潮汐耗散的贡献。为此，我们进行了一套广泛的笛卡尔流体动力学模拟，模拟了行星一小块区域内旋转的瑞利-巴格纳德对流。我们发现由椭圆不稳定引起的潮汐耗散，当它运行时，与先前没有对流的模拟一致ϵ3。对流运动在大尺度潮汐流中也起着有效的粘性作用，导致持续的潮汐耗散（标度为ϵ2）。我们利用（旋转）混合长度理论推导了有效粘度的标度定律，并发现它们很好地预测了我们模拟中发现的湍流量。此外，我们还研究了快速潮汐时有效粘度的降低，我们观察到它与潮汐频率（ω）的比例为ω−2。我们用mesa计算热木星的内部模型来评估我们的标度定律。我们得出的结论是，旋转降低了对流的长度尺度、速度和有效粘度（尽管在快潮状态下不是这样）。我们估计椭圆不稳定性在热木星的最短周期是有效的，而在巨行星中，湍流对流的有效粘度与惯性波相比可以忽略不计。
Tidal dissipation in star–planet systems can occur through various mechanisms, among which is the elliptical instability. This acts on elliptically deformed equilibrium tidal flows in rotating fluid planets and stars, and excites inertial waves in convective regions if the dimensionless tidal amplitude (ϵ) is sufficiently large. We study its interaction with turbulent convection, and attempt to constrain the contributions of both elliptical instability and convection to tidal dissipation. For this, we perform an extensive suite of Cartesian hydrodynamical simulations of rotating Rayleigh–Bénard convection in a small patch of a planet. We find that tidal dissipation resulting from the elliptical instability, when it operates, is consistent with ϵ3, as in prior simulations without convection. Convective motions also act as an effective viscosity on large-scale tidal flows, resulting in continuous tidal dissipation (scaling as ϵ2). We derive scaling laws for the effective viscosity using (rotating) mixing-length theory, and find that they predict the turbulent quantities found in our simulations very well. In addition, we examine the reduction of the effective viscosity for fast tides, which we observe to scale with tidal frequency (ω) asω−2. We evaluate our scaling laws using interior models of Hot Jupiters computed withmesa. We conclude that rotation reduces convective length-scales, velocities, and effective viscosities (though not in the fast tides regime). We estimate that elliptical instability is efficient for the shortest period Hot Jupiters, and that effective viscosity of turbulent convection is negligible in giant planets compared with inertial waves.