Unraveling the Runaway Electron Distribution Emitted by Lightning and Laboratory Discharges

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项目编号	1917069
	Unraveling the Runaway Electron Distribution Emitted by Lightning and Laboratory Discharges
	Caitano da Silva (Principal Investigator)
主持机构	New Mexico Institute of Mining and Technology
项目开始年	2019
	2019-09-01
项目结束日期	2022-08-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	343976(USD)
国家	美国
语种	英语
英文摘要	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.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/213737
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Caitano da Silva .Unraveling the Runaway Electron Distribution Emitted by Lightning and Laboratory Discharges.2019.