Non-linear tides in a homogeneous rotating planet or star: global simulations of the elliptical instability
Non-linear tides in a homogeneous rotating planet or star: global simulations of the elliptical instability
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DOI：
10.1093/mnras/stw702
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发表时间：
2016-03
影响因子：
4.8
通讯作者：
A. Barker
中科院分区：
文献类型：
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作者：
A. Barker
我目前的结果，从第一个全球流体动力学模拟的椭圆不稳定性在潮汐变形的气态行星（或星星）与自由表面。椭圆不稳定性对最短周期热彗星的潮汐演化具有潜在的重要意义。我的模型作为一个自旋轨道对齐或反对齐，非同步旋转，潮汐变形，均匀的流体体的行星。另一份配套文件分析了这种行星的全球模式和不稳定性。在这里，我专注于椭圆形不稳定性的非线性演化。据观察，这会产生湍流的爆发，以不稳定的方式驱动行星与其轨道同步。如果行星的自旋最初是反对齐的，那么椭圆不稳定性也会在类似于自旋同步的时间尺度上驱动自旋轨道对齐。不稳定性在行星内部以纬向流的形式产生差异旋转，这在不稳定性的饱和和产生观测到的突发性方面起着重要作用。这些结果与使用局部笛卡尔模型获得的图像大致一致（其中柱状涡起到了纬向流的作用）。我还模拟了刚性（但无应力）而不是自由容器中的不稳定性，发现了广泛的定量一致性。椭圆不稳定性导致的耗散可以解释为什么最短周期的热彗星倾向于在2-3 d内有圆形轨道，并预测自旋同步（和自旋轨道对齐）大约在10-15 d。然而，必须援引其他机制来解释较长轨道周期的潮汐循环。
I present results from the first global hydrodynamical simulations of the elliptical instability in a tidally deformed gaseous planet (or star) with a free surface. The elliptical instability is potentially important for tidal evolution of the shortest-period hot Jupiters. I model the planet as a spin–orbit aligned or anti-aligned, and non-synchronously rotating, tidally deformed, homogeneous fluid body. A companion paper presented an analysis of the global modes and instabilities of such a planet. Here I focus on the non-linear evolution of the elliptical instability. This is observed to produce bursts of turbulence that drive the planet towards synchronism with its orbit in an erratic manner. If the planetary spin is initially anti-aligned, the elliptical instability also drives spin–orbit alignment on a similar time-scale as the spin synchronization. The instability generates differential rotation inside the planet in the form of zonal flows, which play an important role in the saturation of the instability, and in producing the observed burstiness. These results are broadly consistent with the picture obtained using a local Cartesian model (where columnar vortices played the role of zonal flows). I also simulate the instability in a container that is rigid (but stress-free) rather than free, finding broad quantitative agreement. The dissipation resulting from the elliptical instability could explain why the shortest-period hot Jupiters tend to have circular orbits inside about 2–3 d, and predicts spin synchronization (and spin–orbit alignment) out to about 10–15 d. However, other mechanisms must be invoked to explain tidal circularization for longer orbital periods.