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

该项目的目标是使用数值模拟来设计和分析世界上最高能量的激光设施的实验，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，在天体物理现象中发挥着关键作用，比如河外带电粒子的加速，宇宙射线可以达到比世界上能量最高的粒子加速器大型强子对撞机所获得的能量大10亿倍的能量。然而，宇宙磁场的起源还没有完全被理解。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。然后，当宇宙射线与纠缠的磁场随机散射时，磁化的湍流会调节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，但在地面实验室中极难重现。这个项目的目标是设计和模拟激光驱动的实验，这些实验将首次在实验室中演示(1)辐射、可压缩区域中的湍流发电机机制，以及(2)带电粒子在磁化湍流中通过二阶费米加速而加速。这些实验将在罗切斯特激光能量学实验室的欧米茄激光设施、劳伦斯利弗莫尔国家实验室的国家点火设施(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。这些实验将通过使用由芝加哥大学开发的高性能辐射磁流体动力学程序Flash的模拟活动和在Argonne国家实验室的Mira BG/Q超级计算机上的大规模三维模拟来设计。这些模拟对于确保激光驱动的实验达到运行这些过程所需的等离子体条件、确定何时启动诊断以及解释实验结果至关重要。该项目的结果将引起等离子体和天体物理学团体的广泛关注。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.