Dynamics of Accretion Disks around Magnetized Stars

吸积磁化的恒星，如经典T-金牛座恒星(CTTS)、激变变星和X射线脉冲星，可能具有动态重要的磁场，可以扰乱吸积盘。先前由美国国家科学基金会支持的开创性模拟表明，吸积磁化恒星可能处于稳定或不稳定的吸积区域，具有不同的观测性质(有序或随机光曲线)。如果圆盘靠近恒星，它会通过边界层相互作用，那里的模拟已经显示出开尔文-赫姆霍兹类型的不稳定性。虽然这些模拟和相关的理论分析显示了许多有趣的特征，可以与观测相比较，但仍有必要进一步研究磁盘-磁层/磁盘-恒星相互作用，包括某种类型的磁旋转不稳定(MRI)的可能性。这个新项目包括用2.5D和3D Godunov类型的代码模拟磁盘-磁层相互作用，以模拟相对较薄的磁盘中由MRI驱动的吸积。相关的理论分析将使我们更深入地了解磁盘-磁层/磁盘-恒星边界上的不同类型的不稳定性。由于CTTS在旋转时间尺度上显示了多个可变性特征，因此它们是光度学和光谱光曲线，将与模拟进行比较。光谱建模将使用3D蒙特卡罗辐射传输代码。这项研究将1)研究核磁共振驱动的磁化星吸积；2)从理论和数值上研究盘-磁层和盘-星边界的不同不稳定性；3)将模拟的光曲线和光谱与在不同的CTTS中观测到的光曲线和光谱进行比较。结果将适用于不同的磁化星，包括CTTS、激变变星、吸积棕矮星和吸积中子星。这项研究将提供一个有益的例子，将最先进的2.5D和3D磁化恒星模型与现有的最佳观测结果进行比较。该项目将培训本科生和研究生，以及这一现代多维磁流体力学领域的博士后研究助理。结果将被包括在给本科生、在校学生和康奈尔大学的公众访客的讲座中。最近开发了动画可视化，并将在各种演讲中使用。该团队还为汤普金斯县科学博物馆的一个展览提供支持。

Accreting magnetized stars, such as Classical T Tauri stars (CTTSs), cataclysmic variables, and X-ray pulsars may have dynamically important magnetic fields that can disrupt the accretion disk. Prior NSF-supported pioneering simulations have shown that accreting magnetized stars may be in stable or unstable regimes of accretion with different observational properties (ordered or stochastic light-curves). If the disk comes close to the star, it interacts through the boundary layer, where simulations have shown Kelvin-Helmholtz-type instabilities. Although these simulations and associated theoretical analyses show many interesting features which could be compared with observation, there is a need further to investigate the disk-magnetosphere/disk-star interaction, including the possibility of some type of Magneto-Rotational Instability (MRI). This new project includes simulations of the disk-magnetosphere interaction specifically tailored with 2.5D and 3D Godunov-type codes to model MRI-driven accretion in relatively thin disks. Associated theoretical analysis will give a deeper understanding of different types of instabilities at the disk-magnetosphere/disk-star boundaries. Because CTTSs show multiple variability features in rotation timescales, theirs are the photometric and spectral light-curves that will be compared with simulations. Spectrum modeling will use a 3D Monte Carlo radiative transfer code. This study will 1) investigate MRI-driven accretion onto a magnetized star; 2) investigate, theoretically and numerically, different instabilities at the disk-magnetosphere and disk-star boundaries; and 3) compare simulated light-curves and spectra with those observed in different CTTSs.The results will apply to different magnetized stars, including the CTTSs, cataclysmic variables, accreting brown dwarfs and accreting neutron stars. The research will provide a salutary example of comparing state-of-the-art 2.5D and 3D models of magnetized stars with the best available observations. The project will train undergraduate and graduate students and a postdoctoral research associate in this modern area of multidimensional magneto-hydrodynamics. Results will be included in lectures to undergraduate students, to school students, and to Cornell's public visitors. Animated visualizations have recently been developed and will be used in various talks. The team also supports an exhibit in the Tompkins County Science Museum.