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

这项研究将探索一种诱人的新机制，以解释物质向内流动和它所落在的中心物体之间的区域内的活动。 详细的数值计算工作首次包括所有相关的物理成分，将预测应该观察到什么。 在花了很长时间研究根本行不通的想法之后，该项目有望最终取得进展，并将在这一前沿研究课题上培养学生。天体物理吸积通常会在具有表面的中心物体上进行，在这种情况下，在圆盘的内部边缘形成边界层。 在这一层的能量释放显着影响吸积物体的光谱和可变性，这需要一个良好的工作模型的边界。 该项目始于最近发现的一个重要的新机制，角动量和质量输运通过该地区。 传输机制来自超音速剪切流，产生了全球声波，消散在弱冲击。 它似乎非常有效和强大，需要进一步研究。 这项工作将确定和探索的声学模式在全三维，磁流体动力学（MHD）边界层，其中辐射传输和/或辐射压力的影响是重要的属性。 这项研究涉及详细的模拟使用三维（3D）MHD代码和仔细的分析结果，试图找到简单的物理动机模型的声学模式驱动的运输。 这项工作的高潮是一组模拟，结合了这些先前探索的物理成分。 这种参数空间探索，以了解全球的几何形状和边界层的特性从来没有做过，并将导致直接预测的可观测量。 这些计算将是边界层结构和演变的第一个自洽模型，而不依赖于特定的角动量输运公式，该项目将特别努力招收少数民族和代表性不足群体的学生，培养未来成功的高素质人才。 这些模拟将产生适合公众、公共会谈和一般外联目的的可视化效果。

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.