Tidally Excited Inertial Waves in Stars and Planets: Exploring the Frequency-dependent and Averaged Dissipation with Nonlinear Simulations
Tidally Excited Inertial Waves in Stars and Planets: Exploring the Frequency-dependent and Averaged Dissipation with Nonlinear Simulations
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DOI：
10.3847/2041-8213/acf49f
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发表时间：
2023-09
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影响因子：
--
通讯作者：
A. Astoul;A. Barker
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作者：
A. Astoul;A. Barker
我们模拟的非线性流体动力学演化的潮汐激发的惯性波在对流信封的旋转恒星和巨行星建模为球壳包含不可压缩的，粘性的，分层流体。这个模型对于研究近距离行星和它们的恒星之间的潮汐相互作用，以及近距离低质量星星双星是相关的。我们详细探讨了从一系列广泛的数值模拟中获得的频率相关的潮汐耗散率，我们将其与线性理论进行比较，包括广泛采用的频率平均形式主义来表示惯性波耗散。我们表明，频率平均的预测似乎是相当强大的，近似再现在我们的非线性模拟跨越惯性波的频率范围，因为我们改变对流包络厚度，潮汐振幅，和埃克曼数。然而，我们发现非线性模拟可以产生显着的差异与线性理论为一个给定的潮汐频率（可能由数量级），主要是由于潮汐发电的差异旋转及其对波浪的影响。由于给定系统中的耗散在线性和非线性模拟中可能非常不同，因此应谨慎使用频率平均形式主义。尽管它的鲁棒性，它也不清楚如何准确地代表潮汐演变的真实的（频率依赖）系统。
We simulate the nonlinear hydrodynamical evolution of tidally excited inertial waves in convective envelopes of rotating stars and giant planets modeled as spherical shells containing incompressible, viscous, and adiabatically stratified fluid. This model is relevant for studying tidal interactions between close-in planets and their stars, as well as close low-mass star binaries. We explore in detail the frequency-dependent tidal dissipation rates obtained from an extensive suite of numerical simulations, which we compare with linear theory, including with the widely employed frequency-averaged formalism to represent inertial wave dissipation. We demonstrate that the frequency-averaged predictions appear to be quite robust and are approximately reproduced in our nonlinear simulations spanning the frequency range of inertial waves as we vary the convective envelope thickness, tidal amplitude, and Ekman number. Yet, we find nonlinear simulations can produce significant differences with linear theory for a given tidal frequency (potentially by orders of magnitude), largely due to tidal generation of differential rotation and its effects on the waves. Since the dissipation in a given system can be very different both in linear and nonlinear simulations, the frequency-averaged formalism should be used with caution. Despite its robustness, it is also unclear how accurately it represents tidal evolution in real (frequency-dependent) systems.