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首页> 外文期刊>Earth, planets and space: EPS >Spatial structure and coherent motion in dense planetary rings induced by self-gravitational instability
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Spatial structure and coherent motion in dense planetary rings induced by self-gravitational instability

机译：自重失稳引起的致密行星环的空间结构和相干运动

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We investigate the formation of spatial structure in dense, self-gravitating particle systems such as Saturn's B-ring through local N-body simulations to clarify the intrinsic physics based on individual particle motion. In such a system, Salo (1995) showed that the formation of spatial structure such as wake-like structure and particle grouping (clump) arises spontaneously due to gravitational instability and the radial velocity dispersion increases as the formation of the wake structure. However, intrinsic physics of the phenomena has not been clarified. We performed local N-body simulations including mutual gravitational forces between ring particles as well as direct (inelastic) collisions with identical (up to N approx 40000) particles. In the wake structure particles no longer move randomly but coherently. We found that particle motion was similar to Keplerian motion even in the wake structure and that the coherently motion was produced since the particles in a clump had similar eccentricity and longitude of perihelion. This coherent motion causes the increase and oscillation in the radial velocity dispersion. The mean velocity dispersion is rather larger in a more dissipative case with a smaller restitution coefficient and/or a larger surface density since the coherence is stronger in the more dissipative case. Our simulations showed that the wavelength of the wake structure was approximately given by the longest wavelength #lambda#_(cr)-4 #pi#~2 G sum /#kappa#~2 in the linear theory of axisymmetric gravitational instability in a thin disk, where G, sum, and #kappa# are the gravitational constant, surface density, and a epicyclic frequency.
机译：我们通过局部N体模拟研究了稠密的，自重粒子系统（如土星的B环）中空间结构的形成，以阐明基于单个粒子运动的内在物理。在这样的系统中，Salo（1995）指出，由于重力的不稳定性，空间结构的形成（如尾流状结构和粒子群（团块））是自发产生的，并且径向速度的色散随尾流结构的形成而增加。但是，该现象的内在物理学尚未阐明。我们进行了局部N体模拟，包括环形粒子之间的相互引力以及与相同（最多N约40000）粒子的直接（非弹性）碰撞。在尾流结构中，粒子不再随机地而是连贯地移动。我们发现，即使在尾流结构中，粒子运动也类似于开普勒运动，并且由于团块中的粒子具有相似的偏心率和近日点经度，因此产生了相干运动。这种相干运动引起径向速度色散的增加和振荡。平均速度色散在耗散较大的情况下具有较小的恢复系数和/或较大的表面密度，这是因为在耗散较大的情况下，相干性较强。我们的模拟表明，在薄轴对称重力不稳定性线性理论中，尾波结构的波长大约由最长波长#lambda #_（（cr）-4＃pi＃〜2 G sum /＃kappa＃〜2）给出。盘，其中G，sum和＃kappa＃是重力常数，表面密度和周转频率。

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