难熔包裹体的径向运移及其在死区中的保存
Radial transport of refractory inclusions and their preservation in the dead zone
摘要：
富钙铝包体（CAIs）是已知原始陨石中最古老的太阳系固体。它们比其他成分早1- 200万年，并且可能在很短的时间间隔内在靠近太阳的气态原行星盘中凝结。它们的保存必须平衡由气体拖曳引起的向日漂移和夹带气体的一般向内运动。我们建议，一个有效的向外运输的CAIs可以实现平流作为一个结果的粘性膨胀的磁盘，只要它最初是小于10 AU的大小，我们认为这是合理的从观测和理论的角度来看。气体阻力将在$10^5$年内停止这种向外运动。然而，到那时，随着引力不稳定性的消失，磁死区将会发展，这将使CAIs在磁盘寿命的很大一部分中被困，因为平流速度降低。死区也会阻止随后凝聚的CAIs向外扩散，导致观察到的年龄范围狭窄。这种保存机制是独立的向外传输的情况下（在死区形成之前）和考虑在吸积盘的湍流源的自然结果。
英文摘要：
Calcium-aluminum-rich inclusions (CAIs) are the oldest solar system solids known in primitive meteorites (chondrites). They predate the other components by 1-2 Myr, and likely condensed within a short time interval, close to the Sun in the gaseous protoplanetary disk. Their preservation must counterbalance both the sunward drift caused by gas drag and the general inward motion of the entraining gas. We propose that an efficient outward transport of CAIs can be achieved by advection as a result of the viscous expansion of the disk, provided it is initially less than 10 AU in size, which we argue is plausible from both observational and theoretical points of view. Gas drag would stop this outward motion within $10^5$ yr. However, by that time, a magnetically dead zone would have developed as gravitational instabilities fade away, which would trap CAIs for a significant fraction of the disk lifetime because of the reduced advection velocities. The dead zone would also prevent outward diffusion of subsequently condensed CAIs, contributing to their observed narrow age range. This preservation mechanism is independent of the outward transport scenario (before the dead zone formation) and a natural consequence of considering the source of turbulence in accretion disks.
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