在湍流原行星盘中由凝聚和碎裂引起的富钙-铝夹杂物的生长：观测和模型化
Growth of calcium-aluminum-rich inclusions by coagulation and fragmentation in a turbulent protoplanetary disk: observations and modelisation
摘要：
虽然人们普遍认为南极陨石中的富钙铝包体（CAIs）是在太阳原行星盘的热环境中形成的，但其形成条件仍存在争议。最近的实验室研究CAIs提供了一种新的数据：它们的大小分布。我们发现，在实验室中测量的CAIs的尺寸分布从碳质方解石的截面具有幂律的尺寸分布与累积尺寸指数之间的-1.7和-1.9，这转化为累积尺寸指数之间的-2.5和-2.8经切片校正。为了解释这些观测结果，进行了数值模拟，以探索从微米到厘米尺寸的CAIs的生长，在一个热的和湍流的原行星盘通过凝聚和碎裂的竞争。我们发现，在生长模拟中得到的尺寸分布与陨石中的CAIs尺寸分布一致。我们解释说，如果撞击速度大于10米/秒，CAI碎片的尺寸分布在厘米尺寸处的急剧截止是著名的碎裂障碍的直接结果。毫米和厘米大小的CAIs的生长/破坏时间尺度与当地的尘埃/气体比成反比，在1300 K下约为10年，在1670 K下可达104年。这意味着最难治性的CAIs预计尺寸较小，因为与不太难治性的CAIs相比，它们的生长时间较长。相反，在CAI生产时代，最不耐火的CAI可能已经被回收多次，这可能对它们的辐射年龄产生深远的影响。
英文摘要：
Whereas it is generally accepted that calcium-aluminum-rich inclusions (CAIs) from chondritic meteorites formed in a hot environment in the solar protoplanetary disk, the conditions of their formation remain debated. Recent laboratory studies of CAIs have provided new kind of data: their size distributions. We show that size distributions of CAIs measured in laboratory from sections of carbonaceous chondrites have a power law size distribution with cumulative size exponent between -1.7 and -1.9, which translates into cumulative size exponent between -2.5 and -2.8 after correction for sectioning. To explain these observations, numerical simulations were run to explore the growth of CAIs from micrometer to centimeter sizes, in a hot and turbulent protoplanetary disk through the competition of coagulation and fragmentation. We show that the size distributions obtained in growth simulations are in agreement with CAIs size distributions in meteorites. We explain the CAI sharp cut-off of their size distribution at centimeter sizes as the direct result from the famous fragmentation barrier, provided that CAI fragment for impact velocities larger than 10 m/s. The growth/destruction timescales of millimeter- and centimeter-sized CAIs is inversely proportional to the local dust/gas ratio and is about 10 years at 1300 K and up to 104 years at 1670K. This implies that the most refractory CAIs are expected to be smaller in size owing to their long growth timescale compared to less refractory CAIs. Conversely, the least refractory CAIs could have been recycled many times during the CAI production era which may have profound consequences for their radiometric age.
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