Charged particle depletion surrounding Saturn's F ring - Evidence for a moonlet belt?
Charged particle depletion surrounding Saturn's F ring - Evidence for a moonlet belt?
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土星 F 环周围的带电粒子耗尽 - 小卫星带的证据？
DOI：
10.1016/0019-1035(88)90043-7
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发表时间：
1988
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：
J. Cuzzi;J. Burns
先驱者11号探测到土星F环周围2000公里宽的磁层电子通量的五次突然耗尽。我们重新考虑这些意见，使用改进的描述磁层和已知的环和卫星的位置。我们发现，两个观察到的五个突然减少的电子通量可能是由于吸收已知的F环。然而，其他三个都不太可能是由F环，它的“牧羊人”（潘多拉和普罗米修斯）或共享轨道的物质引起的。我们推断，观测到的带电粒子的耗尽是由低光学厚度（τ 10−4−10−3）的物质团块引起的;我们假设这些团块是由风化层喷出物组成的，是由一个小卫星尺度和更小（半径为0.1-10 km）的看不见的物体带内的碰撞造成的，该带占据了潘多拉和普罗米修斯之间的整个径向区域。我们已经开发了一个自洽的方案，其中这些碎片云的创建，纵向蔓延，并扫到表面上的带对象，只有被抛出再次在随后的碰撞。在这个框架内，微特征吸收器是这样一个物体带中“典型”碰撞的结果，而旅行者图像中显示的搁浅，编织的F环可能是其一些最大，数量最少的成员之间的不太常见的碰撞的结果。假设的带状天体有陡峭的幂律分布，总光学厚度约为10− 4至10−3。我们预计，天王星和海王星的环系统中的一些狭窄的环和环弧可能类似地指示正在进行的碰撞/吸积过程发生在其母行星的洛希区边缘的小卫星带内。
Pioneer 11 detected five abrupt depletions in the flux of trapped magnetospheric electrons within a 2000-km-wide band surrounding Saturn's F ring. We reconsider these observations using an improved description of the magnetosphere and of the locations of known rings and moons. We show that two of the five observed abrupt decreases in electron flux are probably due to absorption by the known F ring. However, none of the other three are likely to be caused by the F ring, its “shepherds” (Pandora and Prometheus), or by material sharing their orbits. We infer that the observed depletions of charged particles are caused by clumps of material with low optical depth (τ ∼ 10−4−10−3); we hypothesize that these clumps are composed of regolith ejecta and result from collisions within a belt of unseen objects of moonlet scale and smaller (0.1–10 km radius) which occupies the entire radial region lying between Pandora and Prometheus. We have developed a self-consistent scenario in which these debris clouds are created, spread longitudinally, and are swept up onto surfaces of the belt objects only to be thrown off again in a subsequent collision. Within this framework, the microsignature absorbers are the outcomes of “typical” collisions in such a belt of objects, while the stranded, braided F ring revealed in Voyager images may be the outcome of a much less common collision between some of its largest, least numerous members. The hypothetical belt objects have a steep powerlaw distribution and a total optical depth of about 10−4to 10−3. We expect that some narrow rings and ring arcs in the ring systems of Uranus and Neptune may be similarly indicative of ongoing collisional/accretional processes taking place within moonlet belts at the edge of the Roche zone of their parent planets.