论文标题
非线性对旋转恒星和行星的对流信封中的潮流的影响
The effects of nonlinearities on tidal flows in the convective envelopes of rotating stars and planets in exoplanetary systems
论文作者
论文摘要
在近距离行星系统中,潮汐相互作用驱动行星和恒星在长时间尺度上驱动轨道和旋转的演变。低质量恒星和巨型气态行星的对流信封中潮汐迫切的惯性波(由科里奥利的加速恢复)在潮汐耗散时会极大地促进潮汐耗散,并随后受阻(例如,通过粘性摩擦),尤其是在系统的早期。已知这些波受到非线性效应的影响,包括以区域流的形式触发差异旋转。在这项研究中,我们使用逼真的潮汐体,强迫通过平衡潮汐在动量方程中的残余作用来激发惯性波。通过在绝热和不可压缩的对流壳中执行3D非线性流体动力学模拟,我们研究了非线性术语的添加如何影响潮流特性,以及能量和角动量重新分布。特别是,我们确定并证明去除了负责在先前数值研究中观察到的非物理角动量进化的术语。在我们的新设置中,我们观察到建立了强圆柱剪切的纬向流,从而改变了先前线性理论预测的潮汐耗散速率。我们证明,这种差异旋转对波的影响整齐地解释了我们许多模拟中线性和非线性耗散率之间的差异。我们还强调了惯性波的旋旋共振和参数不稳定性的主要作用,这些惯性波在影响潮汐流动响应中观察到了足够高的潮汐强迫幅度或低粘度。
In close exoplanetary systems, tidal interactions drive orbital and spin evolution of planets and stars over long timescales. Tidally-forced inertial waves (restored by the Coriolis acceleration) in the convective envelopes of low-mass stars and giant gaseous planets contribute greatly to the tidal dissipation when they are excited and subsequently damped (e.g. through viscous friction), especially early in the life of a system. These waves are known to be subject to nonlinear effects, including triggering differential rotation in the form of zonal flows. In this study, we use a realistic tidal body forcing to excite inertial waves through the residual action of the equilibrium tide in the momentum equation for the waves. By performing 3D nonlinear hydrodynamical simulations in adiabatic and incompressible convective shells, we investigate how the addition of nonlinear terms affects the tidal flow properties, and the energy and angular momentum redistribution. In particular, we identify and justify the removal of terms responsible for unphysical angular momentum evolution observed in a previous numerical study. Within our new set-up, we observe the establishment of strong cylindrically-sheared zonal flows, which modify the tidal dissipation rates from prior linear theoretical predictions. We demonstrate that the effects of this differential rotation on the waves neatly explains the discrepancies between linear and nonlinear dissipation rates in many of our simulations. We also highlight the major role of both corotation resonances and parametric instabilities of inertial waves, which are observed for sufficiently high tidal forcing amplitudes or low viscosities, in affecting the tidal flow response.