Magnetohydrodynamic Simulations of Molecular Cloud Formation

Kritsuk博士和他的团队通过高分辨率数值模拟研究了分子云中磁化湍流和恒星形成的动力学。计算使用了Enzo程序，这是一种自适应网格加密和基于网格的混合程序(流体力学和N-Body)，旨在模拟天体物理和宇宙结构的形成。多相星际介质中可压缩磁流体(MHD)湍流中重力、微分旋转和辐射传输等自洽计算模型对自组织的影响。这里的模型包含了更复杂的物理，更高的分辨率动态范围，并采用了改进的数值方法。特别是对多相MHD湍流的标度及其随湍流磁化强度的变化进行了模拟。对分子云形成的MHD模型的动态范围的模拟利用了千万亿级的计算设备，并试图解决多相星际介质中超音速磁化湍流的惯性范围。当模拟结果与观测结果进行比较时，这将检验相互竞争的恒星形成模型和现象学理论。更广泛地说，为了理解高能粒子的加速和传播、动量和能量在各种天体物理系统中的传输，还需要对湍流有更好的了解。作为该项目的一部分，一名研究生将接受关于超音速MHD流动建模的数值方法的开发、大规模并行计算机模拟以及磁化多相湍流的统计分析和可视化方法的培训。

Dr. Kritsuk and his team study dynamics of magnetized turbulence and star formation in molecular clouds with numerical high-resolution simulations. The computations are done with the Enzo code, an Adaptive Mesh Refinement and grid-based hybrid code (hydrodymamics and N-body), which is designed to do simulations of astrophysical and cosmological structure formation. The self-consistent computations model effects such as gravity, differential rotation, and radiative transfer on the self-organization in compressible magneto-hydrodynamic (MHD) turbulence in the multiphase interstellar medium. The models here incorporate more complex physics, a higher dynamic range of resolved scales, and employ improved numerical methods. In particular, the modeling includes the scaling of multiphase MHD turbulence and its change with the turbulence magnetization. The simulations for the dynamic range of MHD models for molecular cloud formation utilize petascale computational facilities and attempt to resolve the inertial range of supersonic magnetized turbulence in the multiphase interstellar medium. This will test competing star formation models and phenomenological theories when the simulations are compared to observations. More broadly, a better understanding of turbulence is also needed for understanding the acceleration and propagation of energetic particles, transport of momentum and energy in various astrophysical systems. As part of this project, one graduate student will be trained in the development of numerical methods for modeling supersonic MHD flows, in large-scale parallel computer simulations, and in methods for statistical analysis and visualization of magnetized multiphase turbulent flows.