Disk and Wind Accretion to Magnetized Stars

Lovelace，Richard V.AST 0307817大范围的恒星都有显著的磁场。它们通常代表恒星演化的非常早期阶段（所谓的金牛T星），携带有关恒星和原行星盘形成的重要信息，或演化的末期阶段（白色矮星，中子星），由奇异物质组成，并携带有关我们银河系恒星演化路径的信息。这些恒星的可观测性质很大程度上取决于其表面物质的吸积速率，它们周围磁层中物质流动的模式，以及磁力线与周围物质的相互作用。然而，观测不足以理解这些系统中的过程，因为空间细节仍然没有得到解决。磁吸积星星的盘或风的问题也不能用解析法解决。彻底的二维和三维模拟对于理解磁化恒星周围等离子体流的物理特性是必要的。 在这个项目中，研究人员主要集中在几个问题的三维模拟上，这些问题对于理解观测结果很重要。这些包括模拟磁盘吸积到一个星星与偶极磁场在不同的磁极倾角，不同的旋转速率的星星，不同的质量吸积率，吸积直接到一个强或弱磁化星星的模拟。 模拟将提供必要的模型来解释不同天文物体的观测结果。更广泛的影响：这项研究继续吸引许多本科生和研究生。培训学生被认为是整个项目的重要组成部分。通常，四到六名本科生从事项目的不同部分，一到两名研究生从事长期项目，以获得科学研究的经验。 他们学习磁流体力学和编程，使用不同的参数执行模拟运行，并学习如何使用不同的工具分析数据，包括可视化和动画。 所开发的方法和数值代码也具有普遍价值，并适用于其他科学领域：行星科学、地球物理学、磁层科学、太阳科学和工程学。

Lovelace, Richard V.AST 0307817A wide range of stars has significant magnetic fields. They typically represent either very early stages of stellar evolution (so-called T Tauri stars), which carry important information about the formation of stars and protoplanetary disks, or end stages of evolution (white dwarfs, neutron stars), which consist of exotic matter and carry information about the evolutionary paths of stars in our Galaxy. The observable properties of these stars strongly depend on the accretion rate of material to their surface, on the pattern of matter flow in the magnetospheres around them, and on the interaction of magnetic field lines with the surrounding matter. Observations, however, are not sufficient to understand the processes in these systems because the spatial details remain unresolved. Nor can the problem of disk or wind accretion to a magnetized star be solved analytically. Thorough two- and three-dimensional simulations are necessary to understand the physics of plasma flow around magnetized stars. In this project the investigators are concentrating mainly on three dimensional simulations of several problems which are important for the understanding of the observations. These include simulations of disk accretion to a star with a dipole magnetic field at different inclination angles of the magnetic pole, different rotation rates of the star, different mass accretion rates, and simulations of accretion directly to a strongly or weakly magnetized star. The simulations will supply the necessary models to interpret observations of different astronomical objects.Broader impact: This research continues to attract many undergraduate and graduate students. Training students is considered an important part of the overall project. Typically, four to six undergraduate students work on different parts of the project, and one to two graduate students work on longer-term projects gaining experience with scientific research. They learn magnetohydrodynamics and programming, perform simulation runs with different parameters, and learn how to analyze data using different tools including visualization and animation. The developed methods and numerical codes also have general value and are applicable in other areas of science: planetary science, geophysics, magnetosphere science, solar science, and in engineering.