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Unraveling the Runaway Electron Distribution Emitted by Lightning and Laboratory Discharges

解开闪电和实验室放电发射的失控电子分布

基本信息

批准号：
1917069
负责人：
Caitano da Silva
金额：
$ 34.4万
依托单位：
New Mexico Institute of Mining and Technology
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-09-01 至 2024-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1917069&HistoricalAwards=false
关键词：
Unraveling Runaway Electron Distribution Emitted

项目摘要

One of the most fascinating discoveries in atmospheric physics is that thunderstorms may work as particle accelerators, producing intense fluxes of energetic radiation, which take different forms, such as: X-ray flashes emitted from the descending lightning channels, bursts of gamma rays observed at satellite altitudes known as terrestrial gamma-ray flashes (TGFs), and minute-long gamma-ray glows that terminate with a lightning bolt. All of these phenomena are different manifestations of bremsstrahlung emissions of the so-called runaway electrons, which are accelerated to high energies despite the collisions with air molecules. It is theoretically plausible that electron acceleration up to runaway energies (via the so-called thermal runaway electron mechanism) can happen at the tips of lightning channels where strong electric fields exist, but a number of questions about the detailed physics and its implications have puzzled researchers in recent years. Although the key role of runaway electrons in atmospheric electricity has been recognized, to date it remains unsettled whether runaway electrons influence the propagation of lightning and laboratory discharges. It also remains unclear if runaway electrons emitted by lightning leaders can seed TGFs. In some instances, X-ray emissions are observed on the ground and correlated to runaway electrons at the tips of descending lightning leader channels. But in some other occasions, powerful ground TGFs are detected instead. It remains a mystery what kind of lightning discharges produces the more energetic gamma emissions (instead of X-rays) and whether the mechanism involves thermal runaway electron generation. The main project goal is to address this knowledge gap with a robust methodology to infer the flux and spectral energy distribution of runaway electrons emitted by lightning and laboratory discharges. This is a 3-step approach that involves: (1) measuring X-ray emissions from short laboratory discharges that efficiently produce runaway electrons, are repeatable, and the electrical properties can be controlled; (2) developing scalable Monte Carlo simulation codes that can unveil the flux and spectral distribution of runaway electrons when driven/validated by the rich dataset collected in step (1); and (3) performing X-ray observations at the Langmuir laboratory mountain-top facility, leveraging the knowledge acquired from steps (1)-(2) to infer the properties of runaway electrons emitted by natural lightning. Additionally, the project has also an educational aim - the research team will develop a freshman-level classroom module to teach basic concepts of electrical breakdown in air via demonstrations with electrical discharges.This project is jointly funded by NSF Physical and Dynamic Meteorology program and the Established Program to Stimulate Competitive Research (EPSCoR).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.

大气物理学中最令人着迷的发现之一是，雷暴可以作为粒子加速器，产生强烈的高能辐射通量，这些辐射具有不同的形式，例如：从下降的闪电通道发射的X射线闪光，在卫星高度观察到的伽马射线爆发，称为地面伽马射线闪光（TGFs），以及以闪电结束的分钟长的伽马射线辉光。所有这些现象都是所谓的逃逸电子的韧致辐射的不同表现，尽管与空气分子碰撞，这些电子仍被加速到高能量。从理论上讲，电子加速到失控能量（通过所谓的热失控电子机制）可能发生在存在强电场的闪电通道的尖端，但近年来，有关详细物理学及其含义的一些问题一直困扰着研究人员。虽然逃逸电子在大气电中的关键作用已经被认识到，但迄今为止，逃逸电子是否影响闪电和实验室放电的传播仍然没有定论。目前还不清楚闪电先导发射的逃逸电子是否可以播种TGF。在某些情况下，在地面上观察到X射线发射，并与下降的闪电先导通道尖端的失控电子相关。但在其他一些情况下，强大的地面TGF反而被检测到。什么样的闪电放电产生更高能的伽马辐射（而不是X射线）以及这种机制是否涉及热失控电子的产生仍然是一个谜。该项目的主要目标是通过一种强大的方法来推断闪电和实验室放电发射的逃逸电子的通量和光谱能量分布，以解决这一知识差距。这是一种3步方法，包括：（1）测量来自短实验室放电的X射线发射，该放电有效地产生逃逸电子，是可重复的，并且可以控制电特性;（2）开发可扩展的蒙特卡罗模拟代码，当由步骤（1）中收集的丰富数据集驱动/验证时，可以揭示逃逸电子的通量和光谱分布;以及（3）在朗缪尔实验室山顶设施进行X射线观测，利用从步骤（1）-（2）获得的知识来推断自然闪电发射的逃逸电子的性质。此外，本发明还该项目还有一个教育目的--研究小组将开发一个新生级的课堂模块，通过放电演示来教授空气中电击穿的基本概念。该项目由美国国家科学基金会的物理和动力气象学项目以及刺激竞争研究的既定项目（EPSCoR）共同资助该奖项反映了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。

项目成果

期刊论文数量（8）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Relationship Between Sprite Current and Morphology

DOI：
10.1029/2020ja028930
发表时间：
2021-03-01
期刊：
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
影响因子：
2.8
作者：
Contreras-Vidal, L.;Sonnenfeld, R. G.;Stenbaek-Nielsen, H.
通讯作者：
Stenbaek-Nielsen, H.

Data-Driven Simulations of the Lightning Return Stroke Channel Properties

雷电回击通道特性的数据驱动模拟

DOI：
10.1109/temc.2022.3189590
发表时间：
2022
期刊：
IEEE Transactions on Electromagnetic Compatibility
影响因子：
2.1
作者：
Taylor, Michael C.;da Silva, Caitano L.;Walker, T. Daniel;Christian, Hugh J.
通讯作者：
Christian, Hugh J.

Production of runaway electrons and x-rays during streamer inception phase