Between the Disk and the Star: Boundary Layers in Astrophysical Accretion Disks

圆盘和恒星之间：天体物理吸积盘中的边界层

• 批准号: 1515763
• 负责人: Roman Rafikov
• 金额: $ 22.62万
• 依托单位: Institute For Advanced Study
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1515763&HistoricalAwards=false
• 关键词: Between; Disk; Star; Boundary; Layers

This study will explore a tantalizing new mechanism for explaining activity within the region between an inward flow of material and the central object onto which it is falling. Detailed numerical work including for the first time all of the relevant physical ingredients will predict what should be observed. The project promises finally to make progress after a long time spent on ideas that simply did not work, and it will train students in this cutting-edge research topic.Astrophysical accretion often proceeds onto a central object with a surface, in which case a boundary layer forms at the inner edge of the disk. Energy release in this layer dramatically affects the spectra and variability of accreting objects, which requires a good working model of the boundary. This project starts with a recently discovered important new mechanism for angular momentum and mass transport across this region. The transport mechanism comes from supersonic shear flows that give rise to global acoustic waves that dissipate in weak shocks. It appears to be very efficient and robust, and needs to be further studied. This work will identify and explore the properties of acoustic modes in fully three-dimensional, magneto-hydrodynamic (MHD) boundary layers, in which the effects of radiation transfer and/or radiation pressure are important. The study involves detailed simulations using a three-dimensional (3D) MHD code and careful analysis of the results, trying to find simple physically motivated models of transport driven by acoustic modes. The culmination of the work is a set of simulations combining these previously explored physical ingredients. This parameter space exploration to understand the global geometry and characteristics of the boundary layer has never been done before, and will lead to direct prediction of observable quantities. These calculations will be the first self-consistent model of the structure and evolution of boundary layers not relying on ad-hoc angular momentum transport prescriptions.The project will make special efforts to recruit students from minority and underrepresented groups, training personnel highly qualified for future success. The simulations will result in visualizations appropriate for the general public, for public talks and general outreach purposes.

这项研究将探索一种诱人的新机制，以解释材料向内流与其下降的中心物体之间的区域内的活动。 详细的数值工作（包括所有相关物理成分）将预测应观察到的内容。 该项目承诺在花在了很长一段时间的想法上，这根本不起作用，它将在这个尖端的研究主题中培训学生。疏远物理积聚通常会进入具有表面的中心对象，在这种情况下是边界图层在磁盘的内边缘形成。 该层中的能量释放极大地影响了积聚对象的光谱和变异性，这需要一个良好的边界工作模型。 该项目始于最近发现的重要新机制，用于整个该地区的角动量和质量运输。 运输机制来自超音速剪切流，这些剪切流导致全球声波散发出弱冲击。 它似乎非常有效且健壮，需要进一步研究。 这项工作将识别并探索在完全三维的磁磁动力学（MHD）边界层中声学模式的性质，其中辐射转移和/或辐射压力的影响很重要。 该研究涉及使用三维（3D）MHD代码的详细模拟以及对结果的仔细分析，试图找到由声学模式驱动的简单的出于体力动机的运输模型。 工作的高潮是一组模拟，结合了这些先前探索的物理成分。 该参数空间探索以了解边界层的全局几何形状和特征从未做过，并将导致直接预测可观察的数量。 这些计算将是边界层结构和演变的第一个自洽模型，而不依赖于临时角度动量运输处方。该项目将尽力从少数群体和代表性不足的群体中招募学生，培训人员培训非常有资格来实现未来的培训人员成功。 这些模拟将导致适合公众的可视化，以进行公众会谈和一般外展目的。