Saturn's rings, the Yarkovsky effects, and the Ring of Fire
Saturn's rings, the Yarkovsky effects, and the Ring of Fire
复制标题
土星环、雅可夫斯基效应和火环
DOI：
10.1016/j.icarus.2006.05.017
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发表时间：
2004
期刊：
影响因子：
3.2
通讯作者：
D. Rubincam
中科院分区：
文献类型：
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作者：
D. Rubincam
土星的冰环粒子，由于其低导热性，几乎是亚尔科夫斯基效应（由于环上粒子的温度梯度造成的光子推力）的理想操作。这里考察了雅科夫斯基效应的一个极其简单的例子，在这个例子中，轨道演化的计算是假设每个粒子都在一个圆形轨道上单独绕土星运行，这样就没有碰撞、阴影或其他粒子的辐射；也不考虑共振、翻滚或微流星体侵蚀。随机自旋方向的轨道演化似乎是两种效应之间的竞争：使轨道收缩的季节性亚尔科夫斯基效应和使轨道膨胀的亚尔科夫斯基-沙赫效应。远红外和可见光粒子反照率的值（从行星径向计算）沿着轨道的粒子加速度S为负，然后为正，然后又为负；在这个区域，S>0被解释为可能存在稳定环的区域。厘米大小的粒子运行半个土星半径的典型时间尺度是107 - 108年。碰撞、阴影和共振可能会大大延长时间尺度。据推测，由于季节性的亚尔科夫斯基效应，C环可能会耗尽粒子，C环中存在的小粒子最终落在土星上，当它们进入土星大气层时，可能会形成一个“火环”。
Saturn's icy ring particles, with their low thermal conductivity, are almost ideal for the operation of the Yarkovsky effects (photon thrust due to temperature gradients across the ring particles). An extremely simple case of the Yarkovsky effects is examined here, in which orbital evolution is computed as though each particle travels around Saturn alone in a circular orbit, so that there are no collisions, shadowing, or irradiance from other particles; nor are resonances, tumbling, or micrometeoroid erosion considered. The orbital evolution for random spin orientations appears to be a competition between two effects: the seasonal Yarkovsky effect, which makes orbits contract, and the Yarkovsky–Schach effect, which makes orbits expand. There are values of the far infrared and visible particle albedos for which (working radially out from the planet) the along-track particle acceleration S is negative, then positive, and then negative again; the region for which S>0 is interpreted as a region where stable rings are possible. Typical timescales for centimeter-sized particles to travel half a Saturn radius are 107–108yr. Collisions, shadowing, and resonances may lengthen the timescales, perhaps considerably. It is speculated here that the C ring may be depleted of particles because of the seasonal Yarkovsky effect, and small particles that are present in the C ring ultimately fall on Saturn, possibly creating a “Ring of Fire” as they enter the planet's atmosphere.