The formation of chondrules via ablation
The formation of chondrules via ablation
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通过烧蚀形成球粒
DOI：
10.1016/0019-1035(92)90121-m
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发表时间：
1992
期刊：
影响因子：
3.2
通讯作者：
K. Liffman
中科院分区：
文献类型：
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作者：
K. Liffman
我们考虑这样的假设：球粒是流动气流与尺寸比平均球粒大得多的物体相互作用形成的烧蚀产物。我们发现，如果球粒是通过这样的过程形成的，那么气体流速必须小于25 km sec−1，气体密度必须大于10− 8 g cm−3，球粒的最大半径为1 cm，球粒形成体的半径至少为400 m。我们认为，从太阳星云的标准模型，这种类型的球粒形成所需的密度和温度只能在原太阳的大约0.1 Au。在这样的距离下，实验推导出的球粒冷却时间与从高温中面到内太阳星云较冷光球层的传输时间一致，假设传输速度为10至400 km/s。注意到这些速度与观测到的光学喷流和分子外流的流速相似，有人认为这种外流可能产生了球粒，并提供了所需的运输出太阳星云。如果这个想法是正确的，并且如果这些流出物的起源是磁性的，那么只有当流出物的源磁场强度至少为1，000 G时，才有可能形成球粒。
We consider the hypothesis that chondrules are ablation products formed from the interaction of a streaming gas flow with a body whose size is much larger than the average chondrule. We find that if chondrules were formed via such a process, then the gas flow speed would have to be less than 25 km sec−1, the gas densities above 10−8g cm−3, the maximum radius of the chondrule of order 1 cm, and the radius of the chondrule formation bodies at least 400 m. We argue, from a standard model of the solar nebula, that the densities and temperatures required for this type of chondrule formation could only have been found within approximately 0.1 AU of the protosun. At such a distance, the experimentally deduced chondrule cooling times are consistent with transport times from the high-temperature midplane to the cooler photosphere of the inner solar nebula, assuming transport speeds of 10 to 400 km sec−1. Noting the similarity of these speeds to the observed flow speeds of optical jets and molecular outflows, it is suggested that such outflows could have produced chondrules and provided the required transport out of the solar nebula. If this idea is correct and if these outflows are magnetic in origin, then the formation of chondrules was only possible if the outflow had a source magnetic field strength of at least 1,000 G.