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

落在矮星、中子星和黑洞上的物质，这个过程被称为吸积，为一些最有活力和最迷人的天文来源提供了动力。 由于旋转在宇宙中很常见，大多数吸积系统形成围绕中心引力物体旋转的圆盘，在那里物质必须在继续向内之前转移其旋转惯性或角动量。 向内流动的物质也在盘中花费时间将能量转化为向外辐射，通过这些辐射可以观察到这些物体。 这项研究将应用新的方法来理解白色矮星周围盘中的角动量传输过程，并最终解决目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）湍流已经成为理解角动量传输和吸积盘中吸积功率释放的主导研究框架，从原行星盘到活动星系核 虽然最终的目标是模拟观测源，很少有人注意到迄今为止的矮新星爆发吸积盘轨道白色矮星，提供了最有趣的观测约束角动量输运。 使用垂直分层，辐射磁流体动力学（MHD）剪切盒模拟MRI湍流，这项研究将建立在最近的结果显示间歇性热对流。 计划进行三项新研究：（1）确保热对流的数值解析，并了解它如何增强湍流传输，（2）在大部分中性状态下引入非理想MHD，以观察MRI湍流传输是否可以在静止状态下维持;（3）将有关垂直结构和角动量传输的经验教训纳入现有的氢电离盘不稳定性的α模型。 MRI模型和观测之间的直接对抗将巩固氢电离盘不稳定性的理论基础，并允许矮新星和低质量X射线双星的观测更有效地约束MRI湍流的性质。一名研究生将从这个项目中发展他们的论文，几名本科生预计将参与其中，研究将为公开演讲提供信息，包括一个新的一个正在开发的科学专门载于这项工作。

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.