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arXiv 1012.4102astro-ph.EP
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环行星盘的潮汐截断

Tidal Truncation of Circumplanetary Discs

Rebecca G. Martin, Stephen H. Lubow

备注：
Accepted for publication in MNRAS
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摘要：

我们分析了环行星圆盘的一些性质。通过这些圆盘的气流可能为气体巨行星提供大部分质量，这些圆盘可能是形成规则卫星的场所。我们将这些圆盘模拟为受中心恒星潮汐力影响的吸积盘。来自恒星的潮汐力矩移除了靠近盘外缘的盘角动量，并允许吸积盘气体以适合稳定吸积的速率失去角动量。在周期性弹道轨道交叉的半径附近，行星圆盘被截断，圆盘上的潮汐力很强。对于行星希尔半径r_H，该半径出现在大约0.4 r_H处。在金牛座T盘吸积阶段，盘体相当厚，长宽比H/r > 0.2，盘体边缘在~ H ~ 0.1rH范围内逐渐变细。对于一个圆形或稍微偏心的轨道行星，在圆盘的主体内没有明显的共振。然而，潮汐驱动的波涉及共振在截断盘，特别是当它是相当厚的发挥重要作用。我们使用一维的时间相关和稳态模型，也是二维SPH模拟的光盘结构。环行星盘的结构取决于盘湍流粘度随半径的变化，对吸积气体的角分布不敏感。死区可能出现在环行星盘内，并导致密度结构。如果整个圆盘都是湍流的，那么在木星和土星卫星附近的圆盘结构是平滑的，没有明显的特征有利于它们在当前位置形成。

英文摘要：

We analyse some properties of circumplanetary discs. Flow through such discs may provide most of the mass to gas giant planets, and such discs are likely sites for the formation of regular satellites. We model these discs as accretion discs subject to the tidal forces of the central star. The tidal torques from the star remove the disc angular momentum near the disc outer edge and permit the accreting disc gas to lose angular momentum at the rate appropriate for steady accretion. Circumplanetary discs are truncated near the radius where periodic ballistic orbits cross, where tidal forces on the disc are strong. This radius occurs at approximately 0.4 r_H for the planet Hill radius r_H. During the T Tauri stage of disc accretion, the disc is fairly thick with aspect ratio H/r > 0.2 and the disc edge tapering occurs over a radial scale ~ H ~ 0.1 r_H. For a circular or slightly eccentric orbit planet, no significant resonances lie within the main body of the disc. Tidally driven waves involving resonances nonetheless play an important role in truncating the disc, especially when it is fairly thick. We model the disc structure using one dimensional time-dependent and steady-state models and also two dimensional SPH simulations. The circumplanetary disc structure depends on the variation of the disc turbulent viscosity with radius and is insensitive to the angular distribution of the accreting gas. Dead zones may occur within the circumplanetary disc and result in density structures. If the disc is turbulent throughout, the predicted disc structure near the location of the regular Jovian and Saturnian satellites is smooth with no obvious feature that would favor formation at their current locations.

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