Geometric Cross Sections of Dust Aggregates and a Compression Model for Aggregate Collisions
Geometric Cross Sections of Dust Aggregates and a Compression Model for Aggregate Collisions
复制标题
灰尘聚集体的几何横截面和聚集体碰撞的压缩模型
DOI：
10.1088/0004-637x/753/2/115
复制
发表时间：
2012
期刊：
影响因子：
--
通讯作者：
Tom Suyama
中科院分区：
文献类型：
--
作者：
田中有弥;野口裕;石井久夫;岡本卓也;Tom Suyama
尘埃聚集体的几何截面决定了它们与盘状气体的耦合，盘状气体控制着它们在原行星盘中的运动。碰撞结果还取决于初始聚集体的几何横截面。在以前的一篇论文中，我们对由一些亚微米大小的冰粒组成的聚集体的顺序碰撞进行了三维N体模拟，并考察了所获得的聚集体的回转半径(和体积密度)。我们发现，聚集体的碰撞压缩是无效的，聚集体仍然是蓬松的。在本研究中，我们检查了集合体的几何横截面。它们的横截面由于压缩和回转半径而减小。发现了Okuzumi等人提出的截面与回转半径之间的关系。对压缩的聚集体有效。我们还改进了前一篇论文中提出的压缩模型。改进的模型使我们能够计算不断增长的聚集体的回转半径和截面的演化，并很好地再现了我们的连续聚集体碰撞的数值结果。改进后的模型既能描述等质量碰撞，也能描述非等质量碰撞。虽然我们在本研究中没有考虑斜碰撞，但斜碰撞会进一步阻碍集合体的压缩。
Geometric cross sections of dust aggregates determine their coupling with disk gas, which governs their motions in protoplanetary disks. Collisional outcomes also depend on geometric cross sections of initial aggregates. In a previous paper, we performed three-dimensional N-body simulations of sequential collisions of aggregates composed of a number of sub-micron-sized icy particles and examined radii of gyration (and bulk densities) of the obtained aggregates. We showed that collisional compression of aggregates is not efficient and that aggregates remain fluffy. In the present study, we examine geometric cross sections of the aggregates. Their cross sections decrease due to compression as well as to their gyration radii. It is found that a relation between the cross section and the gyration radius proposed by Okuzumi et al. is valid for the compressed aggregates. We also refine the compression model proposed in our previous paper. The refined model enables us to calculate the evolution of both gyration radii and cross sections of growing aggregates and reproduces well our numerical results of sequential aggregate collisions. The refined model can describe non-equal-mass collisions as well as equal-mass cases. Although we do not take into account oblique collisions in the present study, oblique collisions would further hinder compression of aggregates.