CDS&E: Feedback of energetic particles on plasma turbulence

该项目将开发一种新的计算框架，用于模拟高能粒子的天体物理源。在太空中，绝大多数可见物质由热带电气体组成，称为等离子体。等离子体的天体物理流动可以非常快地移动，变成湍流，并产生冲击波。这种等离子体湍流是一系列太空和天体物理问题的关键，包括黑洞吸积盘、超新星爆炸、恒星形成，甚至太空天气。湍流等离子体中的一些粒子通过与湍流运动和冲击波相互作用而获得巨大的能量。在不同的环境中，这些粒子可能被称为宇宙射线、太阳高能粒子或拾取离子。在这些粒子获得能量的同时，它们也改变了激波的结构和湍流的基本特征。在这个项目中，将通过扩展已经成功地用于模拟汽车发动机中湍流燃烧的颗粒相互作用的理论框架，来开发这种相互作用的新的理论模型。将进行最先进的模拟，以研究高能粒子如何改变等离子体湍流和冲击。这些模拟将提供对高能粒子如何通过天体物理等离子体的详细了解，并可能对改进空间天气预报产生实际影响，以帮助将卫星辐射损害降至最低。该项目还将支持在高性能计算中增加学生和专业人员的多样性的努力。等离子体湍流和不稳定性在将粒子加速到高能方面发挥着基本作用。当粒子获得能量时，它们与周围的等离子体相互作用，与某些类型的等离子体波共振，以稳定它们，同时破坏其他类型的等离子体波的稳定，并以尚未完全量化或了解的方式改变背景湍流的特征。这种与湍流背景等离子体的相互作用是许多类型高能粒子加速的关键，这些高能粒子包括高能宇宙射线、太阳高能粒子和拾取离子。在本项目中，通过扩展多组分湍流工程流动和燃烧的最新模型，将产生一个新的模拟多组分可压缩等离子体湍流的计算模型和工具。该模型将自洽地包含等离子体上的高能粒子反馈。这个项目的主要焦点是产生高质量的激波结构和周围湍流的模拟，因为它们被高能粒子修改。这将解决几个悬而未决的问题：(1)高能粒子如何改变激波周围的湍流？(2)高能粒子如何改变激波周围的磁场和磁不稳定性？(3)对激波、湍流和磁不稳定性的修改如何有助于粒子加速？该项目中的模拟还将允许追踪粒子的运动，以产生物理上清晰的理解，了解激波的修改如何影响粒子加速过程。该奖项反映了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。

This project will develop a new computational framework for modeling astrophysical sources of high energy particles. In space, the vast majority of visible matter consists of hot charged gas, called plasma. Astrophysical flows of plasma can move very fast, become turbulent, and generate shock waves. This kind of plasma turbulence is key to a broad range of space and astrophysical problems, including black-hole accretion disks, supernova explosions, star formation, and even space weather. Some of the particles in a turbulent plasma gain enormous amounts of energy by interacting with the turbulent motions, and with shock waves. In different settings, these particles may be called cosmic rays, solar energetic particles, or pick-up ions. While these particles gain energy, they also change the structure of the shock waves, and the fundamental characteristics of the turbulence. In this project a new theoretical model for this interaction will be developed by extending a theoretical framework that has been successfully used to model particle interactions for turbulent combustion in car engines. State-of-the-art simulations will be produced to examine how energetic particles can modify plasma turbulence and shocks. These simulations will provide detailed understanding of how energetic particles move through an astrophysical plasma, and may have a practical impact on improving space weather prediction to help minimize satellite radiation damage. This project will also support efforts to increase diversity among students and professionals in high performance computing.Plasma turbulence and instabilities play a fundamental role in accelerating particles to high energies. As particles gain energy, they interact with the plasma surrounding them, resonating with certain types of plasma waves to stabilize them while destabilizing others, and changing the character of the background turbulence in ways that have not been fully quantified or understood. This interaction with the turbulent background plasma is key to the acceleration of many types of energetic particles including high-energy cosmic rays, solar energetic particles, and pick-up ions. In this project, a new computational model and tool for simulating multi-species compressible plasma turbulence will be produced by expanding on a state-of-the-art model for multi-component turbulent engineering flows and combustion. This model will self-consistently include the energetic particle feedback on the plasma. The main focus of this project is to produce high-quality simulations of the shock structure and surrounding turbulence as they are modified by energetic particles. This will address several open questions: (1) How do energetic particles alter turbulence around a shock? (2) How do energetic particles alter the magnetic field and magnetic instabilities around a shock? (3) How do modifications to shocks, turbulence, and magnetic instabilities contribute to particle acceleration? The simulations targeted in this project will also allow particle movement to be traced to produce a physically-clear understanding of how modification of the shock affects the particle acceleration process.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.