MINERAL PROCESSING BY SHORT CIRCUITS IN PROTOPLANETARY DISKS
MINERAL PROCESSING BY SHORT CIRCUITS IN PROTOPLANETARY DISKS
复制标题
原行星盘中的短路矿物加工
DOI：
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
P. D’Alessio
中科院分区：
文献类型：
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作者：
C. McNally;A. Hubbard;M. Mac Low;D. Ebel;P. D’Alessio
陨石球粒是在太阳系早期由硅酸盐尘埃短暂加热到熔化温度形成的。一些高耐火晶粒（B型富钙铝夹杂物，CAIs）也表现出瞬态加热的迹象。类似的过程也可能发生在其他的原行星盘中，这可以通过观察晶体硅酸盐的光谱特征来证明。这个过程的一个可能的环境是紊流磁流体流体被认为驱动了这些圆盘的吸积。这种流动通常形成薄电流片，这是磁重联的位置，并消散由圆盘发电机放大的磁场。我们认为，在我们最近描述的短路不稳定性集中的电流片中，有可能加热球粒和其他高温矿物的前体颗粒。考虑到不透明度对温度的依赖性，我们扩展了对这一过程的研究，包括辐射冷却的影响；通过在三维磁旋不稳定性的全球模型中检验电流片的几何形状。我们发现1600 K以上的温度可以达到与理想全球模型匹配的有利参数。这种机制可以提供一种有效的方法，利用原行星盘的重力势能，将颗粒加热到足以形成高温矿物的程度。湍流磁重联的体积填充性质与来自球粒-基质互补性、球粒-球粒互补性、火成岩边缘的存在和复合球粒的约束是相容的。同样的短路机制可以在原行星盘中进行其他高温矿物加工，如晶体硅酸盐和cai的生产。
Meteoritic chondrules were formed in the early solar system by brief heating of silicate dust to melting temperatures. Some highly refractory grains (Type B calcium–aluminum-rich inclusions, CAIs) also show signs of transient heating. A similar process may occur in other protoplanetary disks, as evidenced by observations of spectra characteristic of crystalline silicates. One possible environment for this process is the turbulent magnetohydrodynamic flow thought to drive accretion in these disks. Such flows generally form thin current sheets, which are sites of magnetic reconnection, and dissipate the magnetic fields amplified by a disk dynamo. We suggest that it is possible to heat precursor grains for chondrules and other high-temperature minerals in current sheets that have been concentrated by our recently described short-circuit instability. We extend our work on this process by including the effects of radiative cooling, taking into account the temperature dependence of the opacity; and by examining current sheet geometry in three-dimensional, global models of magnetorotational instability. We find that temperatures above 1600 K can be reached for favorable parameters that match the ideal global models. This mechanism could provide an efficient means of tapping the gravitational potential energy of the protoplanetary disk to heat grains strongly enough to form high-temperature minerals. The volume-filling nature of turbulent magnetic reconnection is compatible with constraints from chondrule–matrix complementarity, chondrule–chondrule complementarity, the occurrence of igneous rims, and compound chondrules. The same short-circuit mechanism may perform other high-temperature mineral processing in protoplanetary disks such as the production of crystalline silicates and CAIs.
影响因子：
5.3
作者：
D. Hezel;H. Palme
通讯作者：
D. Hezel;H. Palme