Thermal and photophoretic properties of dust mantled chondrules and sorting in the solar nebula
Thermal and photophoretic properties of dust mantled chondrules and sorting in the solar nebula
复制标题
太阳星云中尘埃球粒的热学和光泳特性及分类
DOI：
10.1051/0004-6361/201218989
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发表时间：
2012
影响因子：
6.5
通讯作者：
G. Wurm
中科院分区：
文献类型：
--
作者：
C. Loesche;G. Wurm
许多陨石球粒被发现是由一个细粒边缘包围。令人怀疑的是，这些边缘是由原行星盘中的陨石球粒所吸积的尘埃获得的。在数值模拟中，我们研究了在照明裸露和尘埃覆盖的球粒的热传递。计算考虑球粒的大小，尘埃地幔的大小，和两个组件的热导率作为参数。我们计算的电泳力和比较的数值结果的解析近似。我们给出了一个表达式来量化的球形颗粒上的电泳力在自由分子政权优于2%。本文用核幔粒子的有效热导率描述了尘埃幔对地幔热膨胀强度的影响。有效热导率主要取决于地幔和球粒的尺寸比，而与绝对尺寸无关。它也强烈地依赖于地幔的热导率，而球粒的热导率的影响很小。其他作者发现陨石的边缘和球粒之间的尺寸比随整体尺寸而系统地变化。在此基础上，我们的计算表明，在光学薄盘或在不断发展的太阳星云的内部边缘的尘埃覆盖的球粒，可以发生的电泳尺寸分选。
Many chondrules are found to be surrounded by a fine grained rim. Supposedly, these rims were acquired from dust accreted to the chondrules in a protoplanetary disk. In numerical simulations we study the heat transfer in illuminated bare and dust mantled chondrules. The calculations consider the chondrule size, the dust mantle size, and the thermal conductivities of both components as parameters. We calculate the photophoretic force and compare the numerical results to analytical approximations. We give an expression to quantify the photophoretic force on a spherical particle in the free molecular regime to better than 2%. We describe the influence of a dust mantle on the photophoretic strength by an effective thermal conductivity of the core-mantle particle. The effective thermal conductivity significantly depends on the size ratio between mantle and chondrule but not on the absolute sizes. It also strongly depends on the thermal conductivity of the mantle with minor influence of the thermal conductivity of the chondrule. The size ratio between rim and chondrule in meteorites is found to vary systematically with overall size by other authors. Based on this, our calculations show that a photophoretic size sorting can occur for dust mantled chondrules in optically thin disks or at the evolving inner edge of the solar nebula.