Constraining the Magneto-Rotational Instability in Accretion Disks with Simulations of Dwarf Novae and X-ray Binary Outbursts

通过模拟矮新星和 X 射线双星爆发来约束吸积盘中的磁旋转不稳定性

• 批准号: 1412417
• 负责人: Omer Blaes
• 金额: $ 23.54万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-06-15 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1412417&HistoricalAwards=false
• 关键词: Constraining; Magneto; Rotational; Instability; Accretion

Material falling onto dwarf stars, neutron stars, and black holes, a process called accretion, powers some of the most energetic and fascinating astronomical sources. Because rotation is common in the Universe, most accretion systems form disks swirling around the central gravitating object, where material must transfer away its rotational inertia, or angular momentum, before continuing inwards. The matter flowing inwards also spends time in the disk converting energy into the outgoing radiation by which these objects can be observed. This research will apply new methods to understanding the process of angular momentum transport in disks around white dwarf stars, and may finally settle whether the currently dominant model is in fact correct.Magneto-rotational instability (MRI) turbulence has become the dominant research framework for understanding angular momentum transport and the release of accretion power in accretion disks across all of astrophysics, from proto-planetary disks to active galactic nuclei. Although the ultimate goal is to model observed sources, little attention has been paid so far to dwarf nova outbursts in accretion disks orbiting white dwarfs, which offer the most interesting observational constraints on angular momentum transport. Using vertically-stratified, radiation magneto-hydrodynamic (MHD) shearing box simulations of MRI turbulence, this research will build on recent results showing intermittent thermal convection. Three new studies are planned: (1) ensure that the thermal convection is numerically resolved, and understand how it enhances turbulent transport, (2) incorporate non-ideal MHD in the largely neutral state to see if MRI turbulent transport can be sustained in the quiescent state; and (3) incorporate lessons learned about the vertical structure and angular momentum transport into existing alpha-based models of the hydrogen ionization disk instability. This direct confrontation between the MRI model and observations will firm up the theoretical foundation of the hydrogen ionization disk instability, and allow observations of dwarf novae and low mass X-ray binaries to constrain more effectively the properties of MRI turbulence.One graduate student will develop their thesis from this project, several undergraduates are expected to be involved, and the research will inform public talks, including a new one being developed specifically on the science contained in this work.

落到矮星、中子星和黑洞上的物质，这一过程称为吸积，为一些最具活力和迷人的天文来源提供动力。 由于旋转在宇宙中很常见，因此大多数吸积系统都会形成围绕中心引力物体旋转的圆盘，其中物质必须先转移掉其旋转惯性或角动量，然后才能继续向内移动。 向内流动的物质也会在圆盘中花费时间将能量转换成向外的辐射，通过这些辐射可以观察到这些物体。 这项研究将应用新方法来理解白矮星周围圆盘中角动量传输的过程，并可能最终确定当前占主导地位的模型是否实际上是正确的。磁旋转不稳定性（MRI）湍流已成为主要研究框架了解从原行星盘到活跃星系核的所有天体物理学中的角动量传输和吸积盘中吸积能量的释放。 尽管最终目标是对观测源进行建模，但迄今为止，人们很少关注围绕白矮星运行的吸积盘中的矮新星爆发，这为角动量传输提供了最有趣的观测限制。 这项研究将基于间歇性热对流的最新结果，利用 MRI 湍流的垂直分层辐射磁流体动力学 (MHD) 剪切箱模拟。 计划进行三项新研究：(1) 确保热对流在数值上得到解析，并了解它如何增强湍流传输，(2) 将非理想 MHD 纳入基本中性状态，以了解 MRI 湍流传输是否可以在静态; (3) 将有关垂直结构和角动量传输的经验教训纳入现有的基于 α 的氢电离盘不稳定性模型中。 MRI 模型和观测结果之间的这种直接对抗将巩固氢电离盘不稳定性的理论基础，并使矮新星和低质量 X 射线双星的观测能够更有效地限制 MRI 湍流的特性。一名研究生将开发他们的论文来自该项目，预计会有几名本科生参与其中，该研究将为公开演讲提供信息，包括专门针对这项工作中所包含的科学开发的新演讲。