Eccentricity Evolution for Planets in Gaseous Disks
Eccentricity Evolution for Planets in Gaseous Disks
复制标题
气态盘中行星的偏心率演化
DOI：
10.1086/346202
复制
发表时间：
2002
期刊：
影响因子：
--
通讯作者：
R. Sari
中科院分区：
文献类型：
--
作者：
P. Goldreich;R. Sari
至少有百分之几的太阳型恒星拥有巨大的行星。令人惊讶的是，大多数都在相当大的偏心率轨道上运行。我们调查的假设，一个巨大的行星和磁盘之间的相互作用，它的形式促进离心率增长。这些相互作用集中在离散Lindblad和共转共振。如果行星的质量足够大，在林德布拉德主共振处的相互作用会导致行星的轨道迁移，并在圆盘中打开一个缺口。一阶林德布拉德共振和共转共振改变了行星的轨道偏心率。偏心率由位于行星同转相反一侧的外部林德布拉德共振的相互作用激发，并由与行星轨道重叠的共轨林德布拉德共振衰减。如果行星清除了圆盘中的间隙，那么由共轨林德布拉德共振引起的偏心阻尼率就会降低。与差距相关的密度梯度通过共转共振以最初略微超过外部Lindblad共振的偏心激励的速率激活偏心阻尼。但是，由于在潜在最大值附近的天平动中捕获了流体，因此可以减小共转力矩。这种非线性饱和可以使平衡倾向于偏心激励。为了克服粘性扩散，需要1%的最小初始偏心率，粘性扩散通过重建大尺度密度梯度来消除共转共振。因此，偏心增长是一种有限振幅不稳定性。形式上，拱点共振是存在于压力主导圆盘中的一种特殊的共轨Lindblad共振，它似乎比外部Lindblad共振更快地阻尼偏心率。然而，在压力主导圆盘中，拱点波的波长很长，以至于它不会传播。自引力主导的圆盘没有拱点共振。然而，拱点波激发间隙边缘。虽然这些传播，他们的长波长表明，他们很可能是在磁盘边缘反射，形成驻波。驻波的粘性阻尼导致偏心阻尼，但其水平远低于行波产生的水平。虽然由于拱点波的偏心阻尼的水平降低到一个适度的水平，在压力和自引力主导的磁盘，它是否下降远低于林德布拉德共振依赖于磁盘的厚度和行星的质量敏感。然而，我们的分析表明，合理的参数，行星盘相互作用可以促进偏心增长。
At least several percent of solar-type stars possess giant planets. Surprisingly, most move on orbits of substantial eccentricity. We investigate the hypothesis that interactions between a giant planet and the disk from which it forms promote eccentricity growth. These interactions are concentrated at discrete Lindblad and corotation resonances. Interactions at principal Lindblad resonances cause the planet's orbit to migrate and open a gap in the disk if the planet is sufficiently massive. Those at first-order Lindblad and corotation resonances change the planet's orbital eccentricity. Eccentricity is excited by interactions at external Lindblad resonances that are located on the opposite side of corotation from the planet, and damped by co-orbital Lindblad resonances that overlap the planet's orbit. If the planet clears a gap in the disk, the rate of eccentricity damping by co-orbital Lindblad resonances is reduced. Density gradients associated with the gap activate eccentricity damping by corotation resonances at a rate that initially marginally exceeds that of eccentricity excitation by external Lindblad resonances. But the corotation torque may be reduced as the result of the trapping of fluid in libration around potential maxima. This nonlinear saturation can tip the balance in favor of eccentricity excitation. A minimal initial eccentricity of the order of 1% is required to overcome viscous diffusion, which acts to unsaturate corotation resonances by reestablishing the large-scale density gradient. Thus, eccentricity growth is a finite-amplitude instability. Formally, the apsidal resonance, which is a special kind of co-orbital Lindblad resonance that exists in pressure-dominated disks, appears to damp eccentricity faster than external Lindblad resonances can excite it. However, the wavelength of the apsidal wave in a pressure-dominated disk is so long that it does not propagate. A self-gravity-dominated disk does not have an apsidal resonance. Nevertheless, apsidal waves are excited at gap edges. Although these propagate, their long wavelengths suggest that they are likely to be reflected at disk edges to form standing waves. Viscous damping of standing waves results in eccentricity damping, but at level far below that which traveling waves would produce. Although the level of eccentricity damping due to apsidal waves is reduced to a modest level in both pressure- and self-gravity-dominated disks, whether it drops well below that of Lindblad resonances depends sensitively on the disk's thickness and planet's mass. However, our analysis shows that with reasonable parameters, planet-disk interactions can promote eccentricity growth.
影响因子：
3.2
作者：
V. Mannings;A. Boss;S. Russell
通讯作者：
V. Mannings;A. Boss;S. Russell