The Dynamics of Planetary Rings
The Dynamics of Planetary Rings
复制标题
行星环的动力学
DOI：
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发表时间：
1982
期刊：
影响因子：
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通讯作者：
S. Tremaine
中科院分区：
文献类型：
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作者：
P. Goldreich;S. Tremaine
天王星和木星周围的环系统的发现，以及先驱者和
旅行者飞船对土星的观测表明，
比之前的推测更常见也更复杂这些
环系统，有趣的是，在他们自己的权利，也作为原型，
大质量的盘系统，如吸积盘和螺旋星系，
在天文学的其他地方。
在旋转系统中，耗散和环是自然的结果。
围绕着一颗球形行星的碎片云沉降成一个扁平的圆环
因为粒子间的碰撞消耗能量，但保持总的角动量，
势头.因为行星是扁圆的，只有角动量的分量
沿着自旋轴的环是守恒的，平环位于赤道
飞机
碰撞重新分配粒子和环之间的角动量
扩散，向内传递质量，向外传递角动量（林登-贝尔
& Pringle 1974）。然而，传播过程发生在一个很大的
比压扁过程更长的时间尺度，
环的速度远低于轨道速度（见第2.2节和第5节。3）。
传播可以通过与卫星的引力相互作用来减缓;然而，
年轮不可能永远存在，对可能的年轮模型的一个重要限制是，它们产生的存活时间至少与年轮的年龄相当。
太阳系（cf.第5、6条）。
这篇评论写于1981年10月，旅行者2号发射后不久
与土星相遇对旅行者号遭遇的数据的分析
但还是完整的因此，在这篇评论的重点是对基本的物理
发生在行星环中的过程，而不是详细的对抗
理论预测与观察的结合
表1列出了已知光环行星的一些重要性质
系统.
为了简洁起见，我们将参考我们写的一系列论文
在环上（Goldreich &特里梅因，1978 a，B，c，1979 a，B，c，1980，1981）作为GT
1，. . .，GT 8。
The discovery of ring systems around Uranus and Jupiter, and the Pioneer and
Voyager spacecraft observations of Saturn, have shown that planetary rings
are both more common and more complex than previously suspected. These
ring systems, interesting in their own right, also serve as prototypes for more
massive disk systems such as accretion disks and spiral galaxies occurring
elsewhere in astronomy.
Disks and rings are a natural consequence of dissipation in rotating systems.
A cloud of debris surrounding a spherical planet settles into a flat circular ring
because interparticle collisions dissipate energy but conserve total angular
momentum. Since planets are oblate, only the component of angular momentum
along the spin axis is conserved, and the flat ring lies in the equatorial
plane.
Collisions redistribute angular momentum among the particles and the ring
spreads, transferring mass inward and angular momentum outward (Lynden-Bell
& Pringle 1974). However, the spreading process occurs on a much
longer timescale than the flattening process since the collision speeds in a flat
ring are much lower than the orbital speeds (see Sections 2.2 and 5. 3).
Spreading can be slowed by gravitational interactions with satellites; nevertheless,
a ring cannot live forever and an important constraint on possible ring models is that they yield survival times at least comparable to the age of the
solar system (cf. Sections 5, 6).
This review was written in October 1981, shortly after the Voyager 2
encounter with Saturn. Analysis of the data from the Voyager encounters is not
yet complete. Therefore the emphasis in this review is on the basic physical
processes that occur in planetary rings, rather than on a detailed confrontation
of theoretical predictions with observation.
Table 1 lists some of the important properties of the planets with known ring
systems.
For the sake of brevity we shall refer to a series of papers we have written
on rings (Goldreich & Tremaine 1978a, b, c, 1979a, b, c, 1980, 1981) as GT
1, . . . , GT 8.