Tree code simulations of planetary rings
Tree code simulations of planetary rings
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行星环的树代码模拟
DOI：
10.1093/mnras/269.2.493
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发表时间：
1994
影响因子：
4.8
通讯作者：
D. Richardson
中科院分区：
文献类型：
--
作者：
D. Richardson
采用局部剪切圆盘模型和四阶积分算法相结合的树型编码方法，对土星B环的动力学问题进行了研究。新的代码，在其他地方详细描述，允许粒子的自重，粒子大小的分布，和表面摩擦（粒子自旋）。对原始代码进行了重要修改，以确保在严重的高密度条件下准确处理碰撞。与Wisdom和特里梅因在等尺寸粒子和平均自引力的情况下的工作相比，显示出极好的一致性。对新的自重力和粒度分布区域进行了相似的分析，结果表明，这些模型的粘性不稳定性条件仍不萨蒂斯艾德。粒子自旋通常位于旋转能量均分包络内，并且在旋转（轨道）框架中平均逆行，但表现出大的结晶度分布。对于大多数模型，固定坐标系中的平均z向自旋在轨道角速度的0.2到0.4倍之间变化，类似于荒木在等尺寸情况下发现的0.3值，而x和y自旋分量通常要小一个数量级。所有三个自旋分量在平衡时都具有洛伦兹分布。结果表明，即使在保守的尺度范围内，也容易形成聚集体，并证实了萨洛报道的引力尾流的发展。有人提出，密度变化中看到的模型，这是迄今为止最现实的，可能部分原因是观察到的土星外环的不均匀性。
A tree code method that incorporates a local shearing disc model and fourth-order integration algorithm is applied to the problem of planetary rings, with particular emphasis on the dynamics of Saturn's B ring. The new code, described in detail elsewhere, allows for particle self-gravity, a distribution of particle sizes, and surface friction (particle spin). Important changes made to the original code, to ensure an accurate treatment of collisions under severe high-density conditions, are described in detail. Comparison with work by Wisdom & Tremaine for the case of equal-size particles and mean self-gravity shows excellent agreement. Similar analysis is performed for the new regimes of selfgravity and particle size distributions, and it is shown that the condition for viscous instability is still not satis ed for these models. Particle spins lie generally within a rotational energy equipartition envelope, and are retrograde on average in the rotating (orbital) frame but exhibit a large spread in obliquity. The mean z-directed spin in the xed frame for most models varies between about 0.2 and 0.4 times the orbital angular velocity, similar to the 0.3 value found by Araki for the equal-size case, while the x and y spin components are generally an order of magnitude smaller. All three spin components have Lorentzian distributions at equilibrium. It is found that aggregates readily form even for conservative size ranges, and the development of gravitational wakes reported by Salo is con rmed. It is proposed that the density variations seen in the models presented, which are the most realistic to date, may account in part for observed non-uniformities in Saturn's outer rings.