Evolution of the Water Snow Line in Magnetically Accreting Protoplanetary Disks
Evolution of the Water Snow Line in Magnetically Accreting Protoplanetary Disks
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DOI：
10.3847/1538-4357/ac06a9
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
S. Mori;S. Okuzumi;M. Kunitomo;X. Bai
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文献类型：
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作者：
S. Mori;S. Okuzumi;M. Kunitomo;X. Bai
太阳系中类地行星的低含水率表明，原始行星是在水雪线内形成的。对雪线位置随时间移动的准确预测为约束行星的形成过程提供了线索。本文研究了层流磁场控制的原行星盘中雪线的迁移，层流磁场是由各种非理想磁流体(MHD)模拟提出的。我们在非理想MHD模拟的基础上提出了一个圆盘温度的经验模型，该模型表明吸积加热的效率明显低于湍流圆盘，并计算了雪线随时间的位置。我们发现，磁吸积层流盘中的雪线在恒星形成后的1Myr内移动到当前地球轨道内，而传统的湍流盘的时间要比1Myr长得多。这一结果表明，要么是在圆盘演化的早期阶段形成的岩石原行星，要么是在靠近原恒星形成后向外移动到当前轨道的原行星。
The low water content of the terrestrial planets in the solar system suggests that the protoplanets formed within the water snow line. Accurate prediction of the snow line location moving with time provides a clue to constraining the formation process of the planets. In this paper, we investigate the migration of the snow line in protoplanetary disks whose accretion is controlled by laminar magnetic fields, which have been proposed by various nonideal magnetohydrodynamic (MHD) simulations. We propose an empirical model of the disk temperature based on our nonideal MHD simulations, which show that the accretion heating is significantly less efficient than that in turbulent disks, and calculate the snow line location over time. We find that the snow line in magnetically accreting laminar disks moves inside the current Earth’s orbit within 1 Myr after star formation, whereas the time for the conventional turbulent disk is much longer than 1 Myr. This result suggests that either the rocky protoplanets formed in such an early phase of the disk evolution, or the protoplanets moved outward to the current orbits after they formed close to the protosun.