Simulations and Theory of Streamer Discharges in Transient Luminous Events

瞬态发光事件中流光放电的模拟和理论

• 批准号: 0734083
• 负责人: Victor Pasko
• 金额: $ 53.42万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-10-15 至 2013-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0734083&HistoricalAwards=false
• 关键词: Simulations; Theory; Streamer; Discharges; Transient

This project is a theoretical investigation of the fundamental properties of streamer discharges in transient luminous events. Transient luminous events are recently discovered large scale optical phenomena occurring at stratospheric and mesospheric/lower ionospheric altitudes in the Earth's atmosphere, which are directly related to electrical activity in underlying thunderstorms. Although a typical transient luminous event may occupy a large overall volume of the upper atmosphere, high spatial resolution imagery of these events reveals many internal and not yet fully understood small scale features, including bright filamentary channels of ionization, or streamers, with transverse spatial scales ranging from tens to hundreds of meters. These streamers are plasma structures which can initiate spark discharges in relatively small gaps in air which is near ground pressures. Streamers are commonly observed with branching structures, but the experimental and theoretical work on understanding the branching mechanism in both transient luminous events and in high pressure applications is still in the preliminary stage. The exact mechanism of streamer branching will be explored and quantified as part of this project, as well as the microphysics of streamers and transient luminous events and their effects on the Earth's atmosphere. This project undertakes a focused effort, including numerical simulations and modeling, which will attack a limited set of current outstanding questions on the fundamental properties of streamer discharges in transient luminous events. The specific scientific questions to be investigated are: (1) What is the initiation mechanism for streamers in low applied electric fields? (2) What are the minimum fields required for the propagation of streamers in air at different pressures? (3) What is the mechanism or mechanisms involved in streamer branching? Answering these questions will quantify more accurately the total volume of atmosphere affected by transient luminous events and the ability of these events to establish a direct path of electrical contact between the troposphere and the mesosphere/lower ionosphere regions. The broader impacts of the proposed activity include the education and training of a graduate student, the support and further training of a post-doctoral scholar, the involvement of undergraduate REU students in research activities related to this project during summer time periods.

本计画系对瞬变发光事件中流注放电之基本特性进行理论研究。 瞬变发光事件是最近发现的发生在地球大气平流层和中层/低电离层高度的大尺度光学现象，它与雷暴中的电活动直接相关。虽然一个典型的瞬变发光事件可能会占据高层大气的很大一部分，但这些事件的高空间分辨率图像揭示了许多内部和尚未完全理解的小尺度特征，包括明亮的电离通道或流光，横向空间尺度从几十到几百米不等。 这些流光是等离子体结构，其可以在接近地面压力的空气中的相对小的间隙中引发火花放电。 流光通常被观察到具有分支结构，但在瞬态发光事件和高压应用中理解分支机制的实验和理论工作仍处于初步阶段。 作为该项目的一部分，将探索和量化流光分支的确切机制，以及流光和瞬态发光事件的微观物理学及其对地球大气层的影响。 该项目进行了集中的努力，包括数值模拟和建模，这将攻击一组有限的当前悬而未决的问题的基本属性的流光放电在瞬态发光事件。 具体的科学问题是：（1）在低电场中，流光的引发机制是什么？ (2)在不同压力下，拖缆在空气中传播所需的最小场是多少？ (3)拖缆分支的机制是什么？ 回答这些问题将更准确地量化受瞬态发光事件影响的大气总量，以及这些事件在对流层和中间层/低电离层区域之间建立直接电接触路径的能力。 拟议活动的更广泛的影响包括研究生的教育和培训，博士后学者的支持和进一步培训，本科REU学生在夏季期间参与与该项目有关的研究活动。