The Physics of Protoplanetesimal Dust Agglomerates. II. Low-Velocity Collision Properties
The Physics of Protoplanetesimal Dust Agglomerates. II. Low-Velocity Collision Properties
复制标题
原行星微尘团块的物理学。
DOI：
10.1086/525841
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发表时间：
2007
期刊：
影响因子：
--
通讯作者：
J. Blum
中科院分区：
文献类型：
--
作者：
Doreen Langkowski;J. Teiser;J. Blum
为了研究原行星尘埃团聚体之间的碰撞，我们进行了微重力实验，研究了高孔隙度毫米级尘埃团聚体对2.5 cm高孔隙度尘埃团聚体的影响。尘埃团聚体由单分散球形、准单分散不规则和多分散不规则微米级尘埃颗粒组成，由随机弹道沉积形成，孔隙率为85% ~ 93%。冲击速度范围为~0.1 ~ ~3 m s−1，冲击角度几乎是随机分布的。除了在实验中形成的靶聚集体表面光滑外，我们还对靶聚集体进行了“模压”，使其局部表面曲率的半径与弹丸半径相对应，从而将靶的孔隙率降低到80%-85%。实验结果表明，对孔隙率最高的靶体的撞击几乎总是导致粘着，而对于孔隙率较低的单分散球形尘粒，中速大角度的碰撞导致弹丸的弹跳，并将质量从靶体传递给弹丸集体。撞击“成型”目标聚集体的粘附概率大大降低。对于光滑目标的撞击，我们测量了侵入的深度和陨石坑的体积，并能够得出一些有趣的动力学特性，这些特性可以帮助推导出原行星微尘聚集体的碰撞模型。未来的原行星盘中聚集体增长模型应该考虑非中心碰撞、碰撞压缩、局部曲率半径对碰撞结果的影响，以及在非粘着碰撞中目标和弹丸聚集体之间可能的传质。
For the investigation of collisions among protoplanetesimal dust aggregates, we performed microgravity experiments in which the impacts of high-porosity millimeter-sized dust aggregates into 2.5 cm high-porosity dust aggregates can be studied. The dust aggregates consisted either of monodisperse spherical, quasi-monodisperse irregular, or polydisperse irregular micrometer-sized dust grains and were produced by random ballistic deposition with porosities between 85% and 93%. Impact velocities ranged from ~0.1 to ~3 m s−1, and impact angles were almost randomly distributed. In addition to the smooth surfaces of the target aggregates formed in our experiments, we “molded” target aggregates such that the radii of the local surface curvatures corresponded to the projectile radii, decreasing the targets' porosities to 80%-85%. The experiments showed that impacts into the highest porosity targets almost always led to sticking, whereas for the less porous dust aggregates, consisting of monodisperse spherical dust grains, the collisions with intermediate velocities and high impact angles resulted in the bouncing of the projectile with a mass transfer from the target to the projectile aggregate. Sticking probabilities for the impacts into the “molded” target aggregates were considerably decreased. For the impacts into smooth targets, we measured the depth of intrusion and the crater volume, and were able to derive some interesting dynamical properties which can help to derive a collision model for protoplanetesimal dust aggregates. Future models of the aggregate growth in protoplanetary disks should take into account noncentral impacts, impact compression, the influence of the local radius of curvature on the collisional outcome, and the possible mass transfer between the target and projectile agglomerates in nonsticking collisions.