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.

该项目是对瞬态发光事件中流媒体放电的基本特性的理论研究。 最近发现了瞬态发光事件，发生在地球大气中的平流层和中层/下层高度处的大规模光学现象，这与潜在雷暴的基础活动直接相关。尽管典型的瞬态发光事件可能会占据大量的上层大气，但这些事件的高空间分辨率图像揭示了许多内部且尚未完全理解的小规模特征，包括电离的明亮丝状通道或流媒体，具有横向空间尺度，范围从数十个到几百米。 这些流媒体是血浆结构，可以在空气中相对较小的空气中引发火花放电，而空气中的空气距离靠近地面压力。 通常使用分支结构观察流媒体，但是在瞬态发光事件和高压应用中了解分支机理的实验和理论工作仍处于初步阶段。 作为该项目的一部分，将探索和量化彩带分支的确切机制，以及彩带和瞬态发光事件的微物理学及其对地球大气的影响。 该项目采取了集中精力的工作，包括数值模拟和建模，这将攻击一组有限的关于瞬时发光事件中流媒体放电基本属性的当前杰出问题。 要研究的具体科学问题是：（1）低应用电场中彩带的启动机制是什么？ （2）在不同压力下，空气中流媒体传播的最小磁场是什么？ （3）流媒体分支中涉及的机制或机制是什么？ 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建立对流层和中层/下电离层区域之间直接接触的直接路径的能力。 拟议活动的更广泛的影响包括对研究生的教育和培训，博士后学者的支持和进一步培训，本科生REU学生参与夏季期间与该项目有关的研究活动。