The equilibrium tide in stars and giant planets: I - the coplanar case
The equilibrium tide in stars and giant planets: I - the coplanar case
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恒星和巨行星的平衡潮汐：I - 共面情况
DOI：
10.1051/0004-6361/201118160
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
J. Zahn
中科院分区：
文献类型：
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作者：
F. Remus;F. Remus;S. Mathis;J. Zahn
自1995年以来，已经发现了500多颗太阳系外行星，它们的轨道非常接近它们的母星星，在那里它们经历了强烈的潮汐相互作用。它们的轨道演变取决于导致潮汐消散的物理机制，而这些机制仍然没有得到很好的理解。我们完善了部分或完全对流的流体体中的平衡潮汐理论，以预测系统的动力学演化。特别是，我们研究的有效性建模的潮汐耗散的品质因数Q，通常是这样做的。我们在这里考虑最简单的情况，即所考虑的星星或行星均匀旋转，所有自旋都是对齐的，伴星被简化为一个质点。潮汐的第一个表现是使星星或行星的形状沿着沿着中心线扭曲。这就产生了绝热平衡潮的无发散速度场，它与动力潮解耦。潮汐动能通过湍流摩擦耗散为热量，在此将湍流摩擦模拟为作用于绝热潮汐流的涡粘性。这种耗散引起了第二个速度场，耗散平衡潮汐，这是在正交的激励潜力，它是负责的虚部的干扰功能，这是实施的动力学演化方程，从中得出的特征演化时间。系统演化的速率取决于潮汐耗散的物理性质，特别是涡动粘度如何随潮汐频率变化以及流体平衡潮汐的对流包络厚度。在低频率下，这种潮汐延迟一个恒定的时间延迟，而它滞后一个恒定的角度时，潮汐频率超过对流周转率。
Since 1995, more than 500 extrasolar planets have been discovered orbiting very close to their parent star, where they experience strong tidal interactions. Their orbital evolution depends on the physical mechanisms that cause tidal dissipation, and these are still not well understood. We refine the theory of the equilibrium tide in fluid bodies that are partly or entirely convective, to predict the dynamical evolution of the systems. In particular, we examine the validity of modeling the tidal dissipation by the quality factor Q, as is commonly done. We consider here the simplest case where the considered star or planet rotates uniformly, all spins are aligned, and the companion is reduced to a point-mass. The first manifestation of the tide is to distort the shape of the star or planet adiabatically along the line of centers. This generates the divergence-free velocity field of the adiabatic equilibrium tide which is decoupled from the dynamical tide. The tidal kinetic energy is dissipated into heat through turbulent friction, which is modeled here as an eddy-viscosity acting on the adiabatic tidal flow. This dissipation induces a second velocity field, the dissipative equilibrium tide, which is in quadrature with the exciting potential; it is responsible for the imaginary part of the disturbing function, which is implemented in the dynamical evolution equations, from which one derives characteristic evolution times. The rate at which the system evolves depends on the physical properties of tidal dissipation, and specifically on how the eddy viscosity varies with tidal frequency and on the thickness of the convective envelope for the fluid equilibrium tide. At low frequency, this tide retards by a constant time delay, whereas it lags by a constant angle when the tidal frequency exceeds the convective turnover rate.