Collaborative Research: Simulating Two-Fluid MHD Turbulence in Star Forming Molecular Clouds on the Blue Waters System

在恒星形成研究中，天体物理学正处于一个数据丰富、模拟丰富的新时代的门槛。恒星如何形成的问题本身就很吸引人，对天体物理学的其他几个领域也有很大的影响。人们普遍认为，银河系中绝大多数恒星的形成都发生在分子云中，特别是巨分子云（GMC）。因此，美国宇航局已经在SOFIA机载天文台的HAWC+等仪器上投入了数百万美元，其具体目标是了解恒星形成云的湍流性质。这个关于蓝水的项目将利用该系统的千万亿级能力，通过模拟NASA仪器目前正在测量的相同过程，来验证恒星形成的理论。该项目将在蓝水上进行模拟，将离子和中性离子结合起来，重现恒星形成的湍流、部分电离气体。由于中性气体不与磁场耦合，但电离气体与磁场耦合，因此该项目建立了模拟双流体等离子体的前沿模拟能力。同时，该项目建立了理论和数值分析工具，可以将模拟与观测进行交叉比较。这种交叉比较为恒星形成理论提供了重要的验证。从模拟中产生的进一步诊断也将用于激发更详细的观察。通过这种方式，蓝水将使理论、计算和详细观察相互支持。此外，该项目打算将计算天体物理学的教育与向更大的天体物理学社区发布模拟工具的代码结合起来。

Astrophysics is at the threshold of a new data-rich and simulation-rich era in star-formation studies. The question of how stars form is fascinating in itself and has a great impact on several other areas of astrophysics. There is a general consensus that a predominant amount of star formation in our Galaxy takes place in molecular clouds, and specifically in giant molecular clouds (GMC). Consequently, NASA has made multi-million dollar investments in instruments such as HAWC+ on the SOFIA airborne observatory with the specific goal of understanding the turbulent nature of star forming clouds. This project on Blue Waters will use the petascale capabilities of the system to validate theories of star formation by simulating the same processes the NASA's instruments are currently measuring.This project will carry out simulations on Blue Waters that integrate the ions and the neutrals to reproduce the turbulent, partially ionized gas in which stars form. Since neutral gas does not couple to the magnetic field, but ionized gas do, the project has built frontline simulation capabilities for simulating two-fluid plasmas. Simultaneously, the project has built theoretical and numerical analysis tools that will enable cross-comparison of simulations with observations. This cross-comparison provides important verification of theories of star formation. Further diagnostics that emerge from the simulations will also be used to motivate more detailed observations. In this fashion, Blue Waters will enable theory, computation and detailed observations to support one another. In addition, the project intends to combine education in computational astrophysics with code releases of their simulation tools to the greater astrophysics community.