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arXiv 1003.1759astro-ph.SR
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原恒星和原行星盘的长期演化。I.爆发

Long-term Evolution of Protostellar and Protoplanetary Disks. I. Outbursts

Zhaohuan Zhu, Lee Hartmann, Charles F. Gammie, Laura G. Book, Jacob B. Simon, Eric Engelhard

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Accepted to publish in ApJ
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摘要：

作为对原恒星盘长期演化的初步研究，我们探索了解释一些年轻恒星中的盘吸积大爆发所需的条件。我们使用一维时间依赖磁盘模型的磁旋转不稳定性（MRI）和引力矩的现象学治疗，以遵循磁盘的演变在很长的时间尺度。与我们以前的二维圆盘模型计算（Zhu et al. 2009 b，Z2009 b）的比较表明，在一维情况下忽略径向效应和二维圆盘结构仅使结果略有差异;这使我们能够使用更简单的模型来有效地探索参数空间。我们发现，通常估计的低质量原恒星的质量下降率通常会导致AU尺度的吸积盘爆发，正如我们以前的分析所预测的那样（Zhu et al. 2009 a，Z2009 a）。我们还证实了准稳态吸积行为的高质量的下落率，如果值的$α$ -参数的磁旋转不稳定性是小的，而在这个高吸积率对流从热不稳定性可能会导致一些变化。我们进一步限制的组合的$α$参数和MRI临界温度，它可以重现观察到的爆发行为。我们的研究结果表明，灰尘升华可能与MRI的完全激活有关。这与小灰尘捕获离子和电子以抑制MRI的想法一致。在以后的论文中，我们将探讨长期的爆发和磁盘的演变与此模型，允许从原恒星信封不同的角动量。

英文摘要：

As an initial investigation into the long-term evolution of protostellar disks, we explore the conditions required to explain the large outbursts of disk accretion seen in some young stellar objects. We use one-dimensional time-dependent disk models with a phenomenological treatment of the magnetorotational instability (MRI) and gravitational torques to follow disk evolution over long timescales. Comparison with our previous two-dimensional disk model calculations (Zhu et al. 2009b, Z2009b) indicates that the neglect of radial effects and two-dimensional disk structure in the one-dimensional case makes only modest differences in the results; this allows us to use the simpler models to explore parameter space efficiently. We find that the mass infall rates typically estimated for low-mass protostars generally result in AU-scale disk accretion outbursts, as predicted by our previous analysis (Zhu et al. 2009a,Z2009a). We also confirm quasi-steady accretion behavior for high mass infall rates if the values of $α$-parameter for the magnetorotational instability is small, while at this high accretion rate convection from the thermal instability may lead to some variations. We further constrain the combinations of the $α$-parameter and the MRI critical temperature, which can reproduce observed outburst behavior. Our results suggest that dust sublimation may be connected with full activation of the MRI. This is consistent with the idea that small dust captures ions and electrons to suppress the MRI. In a later paper we will explore both long-term outburst and disk evolution with this model, allowing for infall from protostellar envelopes with differing angular momenta.

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