Collaborative Research: The Physics of Accretion Disks

Ast-0908336/0908869 Krolik/Hawley由于理解吸积的基本机制是由磁旋转不稳定性驱动的磁流体湍流引起的角动量传输，因此有可能在详细的水平上研究黑洞吸积的天体物理性质。在之前NSF的支持下，这个团队开发了一套牛顿和广义相对论MHD数值模拟代码，适用于探索黑洞吸积流的全球性质及其有时产生的喷流。这个由Krolik博士领导的合作项目现在将扩展之前的工作，以考虑吸积热力学和能量学，大尺度磁场的影响，以及长距离倾斜指向黑洞旋转轴的吸积流如何与Lense-Thirring力矩相互作用。重点将始终放在建立动态模拟数据和可观测性质之间的定量联系上。这项工作应该为关于多少大尺度磁通量可以深入到吸积流中的争论提供真正的指导。它还应该揭示具有内在大尺度结构的磁场所应力的吸积流与那些没有大尺度结构的磁场所产生的吸积流有何不同。此外，计算吸积流中的MHD应力对于研究磁盘在重磁力作用下的弯曲程度是至关重要的，很快就可以用足够的分辨率计算磁盘结构来解决这个问题。来自特定模型的模拟代码和数据将向社会提供，加强了该学科的软件基础设施。该项目将为研究生提供数值模拟技术方面的培训。将继续以模拟结果为基础的成功的公众宣传努力，包括天文表演和电视纪录片。

AST-0908336/0908869Krolik/HawleyArmed by an understanding that the fundamental mechanism of accretion is angular momentum transport due to magnetohydrodynamic (MHD) turbulence driven by the magneto-rotational instability, it has become possible to investigate at a detailed level the astrophysical properties of accretion onto black holes. With previous NSF support, this team has developed a suite of Newtonian and general relativistic MHD numerical simulation codes suitable for exploring the global properties of accretion flows onto black holes and the jets they sometimes generate. This collaborative project, led by Dr. Krolik, will now extend prior work to consider accretion thermodynamics and energetics, the impact of large-scale magnetic fields, and how an accretion flow oriented obliquely to the black hole rotation axis at large distances interacts with Lense-Thirring torques. Emphasis will be placed throughout on creating quantitative links between dynamical simulation data and observable properties.This work should provide genuine guidance for the controversy over how much large-scale magnetic flux may be brought deep into the accretion flow. It should also reveal how accretion flows stressed by magnetic fields with intrinsic large-scale structure may differ from those without. In addition, computing MHD stresses within the accretion flow is essential to the question of the extent of disk bending by gravitomagnetic forces, and it should soon be possible to calculate disk structure with sufficient resolution to address this issue.Both simulation codes and data from specific models will be made available to the community, strengthening the software infrastructure of the discipline. The project will provide graduate student training in numerical simulation techniques. Successful public outreach efforts based on simulation results will continue, including planetarium shows and television documentaries.