Collisions and Gravitational Interactions between Particles in Planetary Rings(Nonequilibrium Dynamics in Astrophysics and Materials Science)
Collisions and Gravitational Interactions between Particles in Planetary Rings(Nonequilibrium Dynamics in Astrophysics and Materials Science)
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行星环中粒子之间的碰撞和引力相互作用（天体物理学和材料科学中的非平衡动力学）
DOI：
10.1143/ptps.195.29
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发表时间：
2012
影响因子：
--
通讯作者：
K. Ohtsuki
中科院分区：
文献类型：
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作者：
K. Ohtsuki
行星环中的粒子围绕中心行星运行，并与其他粒子发生碰撞和引力相互作用。因此，它们的轨道变得倾斜和非圆形。此外，环颗粒可能有粗糙的表面，它们之间的倾斜碰撞导致旋转。在碰撞频率比轨道频率小得多的稀环中，粒子的轨道通过连续的两体碰撞和/或引力相遇而演化，并且该演化可以由基于三体问题的公式描述。我们描述了这种情况下的基本方程，并推导出粒子速度色散和自旋速率的演化方程。我们还讨论了环的自引力的影响，这成为主要的密集环。粒子之间的碰撞和引力相互作用导致行星环中的角动量转移。我们讨论了环的粘性，它决定了在环的角动量转移率。稀环中的粘度可以用粒子的速度色散来表示，并且对于给定的粒子尺寸，粘度与环表面密度成比例，而在致密的自引力环中，粘度对环表面密度的依赖性更强，其中角动量通过引力尾流之间的相互作用传递。
Particles in planetary rings orbit the central planet, and undergo collisions and gravitational interactions with other particles. As a result, their orbits become inclined and non-circular. Also, ring particles likely have rough surfaces, and an oblique impact between them leads to rotation. In the case of dilute rings where collision frequency is sufficiently smaller than the orbital frequency, particles’ orbits evolve through successive two-body collisions and/or gravitational encounters, and the evolution can be described by the formulation based on the three-body problem. We describe basic equations for such cases, and derive evolution equations for particle velocity dispersion and spin rates. We also discuss effects of rings’ self-gravity, which become dominant in dense rings. Collisions and gravitational interactions between particles result in angular momentum transfer in planetary rings. We discuss ring viscosity, which determines the rate of angular momentum transfer in rings. Viscosity in dilute rings can be expressed by particles’ velocity dispersion and is proportional to the ring surface density for a given particle size, while the dependence of the viscosity on ring surface density is stronger in dense self-gravitating rings, where angular momentum is transferred by interactions between gravitational wakes.