CDS&E: Feedback of energetic particles on plasma turbulence

该项目将开发一个新的计算框架，用于模拟高能粒子的天体物理来源。在太空中，绝大多数可见物质由热的带电气体组成，称为等离子体。 天体物理学上的等离子体流可以非常快速地移动，变得湍流，并产生冲击波。 这种等离子体湍流是一系列空间和天体物理问题的关键，包括黑洞吸积盘，超新星爆炸，星星形成，甚至空间天气。 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。 当这些粒子获得能量时，它们也改变了冲击波的结构和湍流的基本特征。 在这个项目中，这种相互作用的一个新的理论模型将开发扩展的理论框架，已成功地用于模拟汽车发动机中的湍流燃烧颗粒相互作用。 将制作最先进的模拟来研究高能粒子如何改变等离子体湍流和冲击。 这些模拟将详细了解高能粒子如何在天体物理等离子体中移动，并可能对改进空间天气预测产生实际影响，以帮助最大限度地减少卫星辐射损害。 该项目还将支持提高学生和专业人员在高性能计算方面的多样性的努力。等离子体湍流和不稳定性在将粒子加速到高能量方面起着根本作用。随着粒子获得能量，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，同时使其他人不稳定，并以尚未完全量化或理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加速许多类型高能粒子的关键，包括高能宇宙射线，太阳高能粒子和拾取离子。 本计画将在目前多组份紊流工程流动与燃烧模型的基础上，发展出一种新的多组份可压缩电浆紊流的计算模型与工具。 该模型将自洽地包括等离子体上的高能粒子反馈。 该项目的主要重点是产生高质量的模拟激波结构和周围的湍流，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)高能粒子如何改变冲击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？ 该项目中的模拟目标还将允许追踪粒子运动，以产生对冲击的修改如何影响粒子加速过程的物理清晰的理解。该奖项反映了NSF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。

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.