Three-Dimensional Numerical Modeling of Sprite Streamers

该奖项将使用最近开发的高性能等离子体放电流体模拟代码，与最新的精灵高速图像密切结合，研究精灵流的基本物理。大约三十年前，人们发现强大的雷击可以在地球上层大气中引起壮观的瞬态发光事件（TLEs）。精灵是游戏中的一种。随后的研究发现，精灵与地面附近的火花放电有着相似的物理特征。然而，它们要大得多，持续时间也长得多，因为它们发生在空气密度大大降低的环境中。精灵可以引起高层大气物理和化学性质的重大改变，能够影响用于远程通信的某些无线电频段的传播。精灵的高分辨率图像显示，它们由大量被称为飘带的等离子体细丝组成。人们已经认识到，理解流光物理是学习精灵动态和效果的关键。该项目将利用先进的计算机模拟工具来研究各种鲜为人知的拖缆过程。它将极大地推进我们对精灵的物理和效果的理解。该研究将促进对介电击穿和瞬态等离子体放电的认识，提高雷电预报和安全。在这个项目中开发的软件将是开源的。研究生和本科生将支持和参与这项研究项目，从而促进STEM劳动力的发展。该项目将研究流子分支、流子头之间的碰撞、流子头与流子通道之间的碰撞、中性密度扰动对流子动力学的影响，以及流子与下部电离层之间的相互作用。将使用最近开发的高性能等离子体放电流体代码AMPLIFI（等离子体启动、成丝和相互作用的自适应建模）进行各种三维模拟，以了解这些过程的物理特性、它们在精灵动力学中的作用、它们的电学和光学效应以及它们对周围环境的依赖。该项目还将为解释精灵的高速图像和理解其含义提供关键信息。将获得精灵流动力学对环境中性或电条件的依赖的具体知识，这将使通过观察精灵来研究中间层/D区电离层的潜在强大遥感方法的发展成为可能。研究中性密度扰动对精灵流光动力学的影响也将揭示一种新的强电场作用下的中性离子耦合机制。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 award will investigate the fundamental physics of sprite streamers using a recently developed, high-performance plasma discharge fluid simulation code, in close conjunction with the latest high-speed images of sprites. About thirty years ago, it was discovered that powerful lightning strokes can cause spectacular Transient Luminous Events (TLEs) in the earth’s upper atmosphere. Sprites are one of the TLEs. Subsequent research has found that sprites share similar physical characteristics as those commonly known spark discharges near the ground. They, however, are much larger and last much longer, because they occur in an environment with greatly reduced air density. Sprites can cause significant modifications of the physical and chemical properties of the upper atmosphere, capable of affecting the propagation of certain radio frequency bands for long-range communications. High-resolution images of sprites have revealed that they consist of a large number of plasma filaments known as streamers. It has been recognized that understanding streamer physics holds the key to learning sprite dynamics and effects. This project will utilize an advanced computer simulation tool to study various poorly understood streamer processes. It will greatly advance our understanding of the physics and effects of sprites. The study will advance knowledge of dielectric breakdown and transient plasma discharges and improve lightning forecast and safety. The software developed in this project will be open source. Graduate and undergraduate students will be supported and involved in this research project, thus contributing to STEM workforce development. This project will investigate streamer branching, collisions between streamer heads, collisions between streamer heads and streamer channels, effects of neutral density perturbations on streamer dynamics, and interaction between streamers and the lower ionosphere. Various three-dimensional simulations will be performed using a high-performance plasma discharge fluid code called AMPLIFI (Adaptive Modeling of PLasma Initiation, Filamentation and Interaction), which was recently developed, to understand the physics of these processes, their roles in sprite dynamics, their electrical and optical effects, and their dependence on the ambient environment. This project will also provide critical information for interpreting high-speed images of sprites and understanding the implications. Concrete knowledge of the dependence of sprite streamer dynamics on ambient neutral or electrical conditions will be obtained, and this will enable the development of potentially powerful remote sensing approaches to studying the mesosphere/D region ionosphere by observing sprites. The study of the neutral density perturbation effects on sprite streamer dynamics will also reveal a novel neutral-ion coupling mechanism enabled by a strong electric field.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.