CDS&E: Feedback of energetic particles on plasma turbulence

这个项目将开发一个新的计算框架来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，变得湍流，并产生激波。这种等离子体湍流是解决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、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激波的相互作用获得了巨大的能量。在不同的情况下，这些粒子可能被称为宇宙射线、太阳高能粒子或吸收离子。当这些粒子获得能量时，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用于模拟汽车发动机湍流燃烧的粒子相互作用的理论框架，来开发这种相互作用的新理论模型。最先进的模拟将用于研究高能粒子如何改变等离子体湍流和冲击。这些模拟将提供高能粒子如何穿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，以帮助最大限度地减少卫星辐射损害。该项目还将支持在高性能计算领域增加学生和专业人员的多样性。等离子体的湍流和不稳定性在粒子加速到高能的过程中起着重要的作用。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而破坏其他类型的等离子体波，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许多高能粒子加速的关键，这些高能粒子包括高能宇宙射线、太阳高能粒子和吸收离子。在这个项目中，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将通过扩展最先进的多组分湍流工程流动和燃烧模型而产生。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？高能粒子如何改变激波周围的磁场和磁不稳定性？(3)冲击、湍流和磁不稳定性的变化如何影响粒子加速？该项目的模拟目标还将允许追踪粒子运动，从而对冲击的改变如何影响粒子加速过程产生物理上清晰的理解。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。

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.