Numerical Modeling of Laser-Driven Experiments to Study Astrophysical Processes in Magnetized Turbulence

该项目的目标是利用数值模拟来设计和分析世界上最具能量的激光设备上的实验，以在实验室中演示和研究高能天体物理过程。磁场存在于整个宇宙中，在天体物理现象中起着至关重要的作用，例如河外带电粒子的加速，宇宙射线的能量可以达到世界上能量最高的粒子加速器大型强子对撞机所达到的能量的十亿倍。然而，宇宙磁场的起源尚不完全清楚。宇宙学家和天体物理学家的共识是，它们是微小种子场放大的结果，这些种子场被天体物理等离子体中的湍流运动拉伸和扭曲——这一过程被称为湍流发电机。当宇宙射线随纠缠的磁场随机散射时，磁化的湍流就会介导宇宙射线的传播和加速。这些天体物理过程在太空中经常发生，但在地球实验室中很难重现。这个项目的目标是设计和模拟激光驱动的实验，这将首次在实验室中证明(1)在辐射、可压缩状态下的湍流发电机机制，以及(2)在磁化湍流中通过二阶费米加速带电粒子的加速。这些实验将在罗彻斯特激光能量学实验室的Omega激光设备、劳伦斯利弗莫尔国家实验室的国家点火设备（NIF）和德国达姆施塔特的GSI亥姆霍兹重离子研究中心进行。这项工作将利用成熟的TDYNO（湍流发电机）实验平台，该平台是在欧米茄和NIF之前非常成功的三年实验活动中开发和部署的。实验将通过使用FLASH（芝加哥大学开发的高性能辐射磁流体动力学代码）和阿贡国家实验室Mira BG/Q超级计算机上的大规模三维模拟来设计模拟活动。模拟对于确保激光驱动实验达到这些过程运行所需的等离子体条件至关重要；确定何时启动诊断；并解释实验结果。该项目的结果将引起等离子体和天体物理学界的广泛兴趣。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to use numerical simulations to design and analyze experiments at the world's most energetic laser facilities to demonstrate and study high energy astrophysical processes in the laboratory. Magnetic fields are present throughout the universe and play critical roles in astrophysical phenomena, such as the acceleration of extragalactic charged particles, cosmic rays which can reach energies that are a billion times larger than those achieved in the Large Hadron Collider, the world's highest-energy particle accelerator. However, the origin of cosmic magnetic fields is not fully understood. The consensus among cosmologists and astrophysicists is that they are the result of the amplification of tiny seed fields, which are stretched and twisted by turbulent motions in astrophysical plasmas -- a process called turbulent dynamo. The magnetized turbulence then mediates the propagation and acceleration of cosmic rays as they randomly scatter with the tangled magnetic fields. These astrophysical processes occur frequently in space but are extremely hard to recreate in terrestrial laboratories. The goal of this project is to design and model laser-driven experiments that will demonstrate for the first time in the laboratory (1) the turbulent dynamo mechanism in the radiative, compressible regime, and (2) the acceleration of charged particles via second-order Fermi acceleration in magnetized turbulence. These experiments will be carried out at the Omega Laser Facility at the Laboratory for Laser Energetics at Rochester, the National Ignition Facility (NIF) at Lawrence Livermore National Laboratory, and the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany. The effort will exploit the mature TDYNO (turbulent dynamo) experimental platform, which was developed and deployed in a prior highly successful three-year experimental campaign at Omega and NIF. The experiments will be designed through simulation campaigns using FLASH, the highly capable radiation magneto-hydrodynamics code developed by the University of Chicago, and large-scale three-dimensional simulations on the Mira BG/Q supercomputer at Argonne National Laboratory. The simulations are critical to ensuring the laser-driven experiments achieve the plasma conditions necessary for these processes to operate; determining when to fire the diagnostics; and interpreting the results of the experiments. The results of the project will be of broad interest to the plasma and astrophysics communities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.