A numerical study of Saturn's F-ring
A numerical study of Saturn's F-ring
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土星 F 环的数值研究
DOI：
10.1016/0019-1035(82)90013-6
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发表时间：
1982
期刊：
影响因子：
3.2
通讯作者：
J. Burns
中科院分区：
文献类型：
--
作者：
M. Showalter;J. Burns
我们研究了在所有天体都沿着偏心轨道运动的一般情况下，“牧羊人”卫星对窄环的短期影响。我们通过数值跟踪测试粒子的环来做到这一点，因为它们的轨道在牧羊人的引力扰动下演化。假定为平面运动。我们的数值方案通过构造一个微扰积分表，然后反复使用它，极大地提高了计算速度(提高了∼的10~4倍)。这种方法适用于任何附近有卫星的窄环，例如由P.Goldreich和S.Tremaine的放牧机制限制的环[Nature277，97-99(1979)]。我们得出了各种轨道构型的结果，然后将这些结果应用于土星的F环。数值积分的几个特征让人想起旅行者号上观察到的扭结和团块。如果环到卫星的距离由于偏心而发生显著变化，那么环可以在跟随卫星的方位角域中分裂成周期性的团块。这个地区在经度上可能有些滞后。扰动还可能导致环的宽度变化很大，在牧羊人最接近的点附近最窄，而在相反的一侧最宽。目前还不清楚这种影响是否在旅行者号的图像中观察到，或者可能观察到。最后，牧羊人的扰动可能会影响环的一个重要的、但可能是时间可变的偏心。短期的趋势不是环和卫星的对准；更长的时间效应还没有被探索。
We study the short-term effects of “shepherding” satellites on narrow rings, in the general case where all bodies move along eccentric orbits. We do this by following numerically a ring of test particles as their orbits evolve under the gravitational perturbations of the shepherds. Planar motion is assumed. Our numerical scheme vastly improves (by a factor of ∼104) the computation speed over conventional orbital integration methods by constructing a table of the perturbation integrals and then utilizing it over and over. The approach is applicable to any narrow ring with a nearby satellite, such as a ring confined by the shepherding mechanism of P. Goldreich and S. Tremaine [Nature277, 97–99 (1979)]. We arrive at results for a variety of orbital configurations, and then apply these to the F-ring of Saturn. Several features of the numerical integration are reminiscent of the kinks and clumps observed by Voyager. If the ring-to-satellite distance changes significantly due to eccentricities, then the ring can break up into periodic clumps in an azimuthal domain which trails the satellite. This region may lag somewhat in longitude. The perturbations may also cause the ring to vary significantly in width, being narrowest near the point of closest approach of the shepherd and widest at the opposite side. It is as yet unclear whether this effect is, or could be, observed in the Voyager images. And finally, the perturbations of the shepherds can impact a significant, but probably time variable, eccentricity to the ring. The short-term tendency is not toward alignment of ring and satellite apsides; longer time effects have not been explored.