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Numerical Investigations of Photoevaporative Disks: Processes relevant to planet and regular satellite formation.

机译：光蒸发盘的数值研究：与行星和常规卫星形成有关的过程。

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摘要

Traditional models of disks around young planets and stars make a number of simplifying assumptions. These include the use of ad hoc radial temperature profiles, or isothermal disks. Another common assumption is in regard to the treatment of the outer boundary, which is allowed to expand to infinity, or neglected completely. There has also been a lack of time-dependent viscous models that include the affects of photoevaporation and/or ongoing accretion. We alleviate many of these issues by adapting numerical methods for solving propagating phase change problems to astrophysical disks in a completely novel way. These models are all viscous, time-dependent models that include a self-consistent treatment of mass loss via photoevaporation at the disk outer edge. In the case of circumplanetary disks, they also include continued accretion from the solar nebula.;I present investigations of disks around young planets and stars, made using a variety of numerical models. The investigations are primarily focused on how disk structure and evolution affect the growth and migration of growing satellite and planetary embryos. Another focus is to assess what, if any, processes are responsible for angular momentum transport in circumplanetary disks. I present detailed descriptions of these models as well as the results of applying these models to both the solar nebula and to disks around giant planets, in which regular satellites formed.;Photoevaporation can substantially truncate disks and has a similar level of affect on disk evolution and morphology as variations in the viscosity parameter, alpha All of the solar nebula models were truncated, yet none of them match the steep radial surface density profile inferred from the compact configuration of the giant planets in the Nice model. Furthermore, photoevaporation has the ability to remove gas and dissipate disks on very short timescales. Despite their evolving nature, we find that giant planets and satellites can form in the evolving disks produced by these models. We conclude that steady-state circumstellar disk models are lacking and the traditional way of treating the outer boundary needs to be reexamined.;With regard to circumplanetary disks, magnetorotational instability is not a viable mechanism for angular momentum transport in the detailed 1+1D model presented here. However, temperature and density dependent opacities produce non-power law radial profiles. The deviations from power-law cause there to be increases in the radial entropy gradient. This allows for the generation of baroclinic instabilities that can be sustained and amplify. These results help alleviate the long-standing problem of angular momentum transport in circumplanetary disks and differentiate between competing models of circumplanetary disk structure.
机译：围绕年轻行星和恒星的磁盘的传统模型做出了许多简化的假设。其中包括使用临时径向温度曲线或等温盘。关于外边界的处理，另一个常见的假设是允许扩展到无穷大或完全被忽略。还缺乏依赖于时间的粘性模型，其中包括光蒸发和/或持续吸积的影响。我们通过采用数值方法以一种全新的方式解决了传播相变问题到天体盘的问题，从而缓解了许多此类问题。这些模型都是粘性的，与时间有关的模型，包括通过磁盘外边缘的光蒸发对质量损失进行的自洽处理。在外行星盘的情况下，它们还包括太阳星云的持续积聚。我用各种数值模型对年轻行星和恒星周围的盘进行了研究。研究主要集中在磁盘结构和演化如何影响正在生长的卫星和行星胚胎的生长和迁移方面。另一个重点是评估，如果有的话，哪些过程负责在行星盘上的角动量传输。我将对这些模型进行详细描述，并将这些模型应用于太阳星云和形成常规卫星的巨型行星周围的盘上的结果;光蒸发可以实质上截断盘，并且对盘演化的影响程度相似和形态作为粘度参数的变化，阿尔法所有的太阳星云模型都被截断，但没有一个与从尼斯模型中的巨型行星的紧凑构型推断出的陡峭的径向表面密度分布相匹配。此外，光蒸发具有在非常短的时间内去除气体并驱散圆盘的能力。尽管它们具有不断发展的性质，但我们发现在这些模型产生的不断演化的磁盘中仍可以形成巨大的行星和卫星。我们得出的结论是，缺少稳态的星际圆盘模型，需要重新研究处理外边界的传统方法。关于周圆盘，在详细的1 + 1D模型中，磁旋转不稳定性不是角动量传输的可行机制。呈现在这里。但是，取决于温度和密度的不透明度会产生非幂定律的径向轮廓。与幂律的偏差导致径向熵梯度增加。这允许产生可以持续和放大的斜压不稳定性。这些结果有助于缓解长期存在的外行星盘角动量传输问题，并区分外行星盘结构的竞争模型。

著录项

  • 作者

    Mitchell, Tyler Robert.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Astrophysics.
  • 学位 Ph.D.
  • 年度 2014
  • 页码 154 p.
  • 总页数 154
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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