CEDAR: High Speed Spectroscopic Studies of lightning bolts: Starters, Jets, and Gigantic Jets

CEDAR：闪电的高速光谱研究：启动器、喷射流和巨型喷射流

• 批准号: 1755513
• 负责人: Ningyu Liu
• 金额: $ 29.84万
• 依托单位: University of New Hampshire
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-05-12 至 2021-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1755513&HistoricalAwards=false
• 关键词: CEDAR; Speed; Spectroscopic; Studies; lightning

The Coupling, Energetics, and Dynamics of Atmospheric Regions (CEDAR) program, a broad-based, community-guided, upper atmospheric research program, seeks to understand the behavior of atmospheric regions from the lower atmosphere upward through the ionized upper layers of the atmosphere. Of particular interest is the question of the scale of coupling of the lower atmosphere, where phenomena such as thunderstorms exist, to the ionized layer near 100-120 km. The physics of lightning phenomenology within thunderstorm events are very complex and highly time-dependent with complex morphology characterizing the coupling of lightning bolts to the ionosphere with consequential significant temporal behavior of the ionized density of the lower ionosphere region. These electrical discharges are initiated inside thunderstorms and are rooted in one of the main thundercloud charge layers. This award would study the physical processes underlying the particular transient lightning bolt structures referred to as blue starters, jets, and gigantic jets, which are the upward electrical discharges from thunderstorms that terminate at 20-30 km, 40-50 km and 70-90 km altitude, respectively. These are generated suddenly within a fraction of a second from thunderstorms. The research supported by this award would examine the energetics and dynamics of these TIL (Transient Luminous Event) phenomena. Typically, the initial vertical development has a speed of ~100 km/s, but after 100-300 ms, the upward discharge leading to gigantic jets suddenly accelerates to reach the lower ionosphere with a speed greater than 1000 km/s. The funded research would be primarily observational involving the construction of a high-speed (5,000 frames per second) spectrograph that can analyze the energetics of the jets and starters through the fast acquisition of visible atomic and molecular spectra allowing high-speed measurements of the relative intensities of the red-to-blue colors emitted by the lightning bolt along its path between the storm and the ionized layer. Analysis of these spectra would provide the time variations of the vertical temperature profile within the ionized air pathway of the lightning bolt. This information about the temperature profile would be used to quantify the energetics underlying the formation of these morphological features of the lightning bolt. This award has the potential of transformative research that would provide a major advance in the knowledge and understanding of the physics of transient plasma discharges which should prove to be extremely valuable and of high importance to the study of laboratory electrical discharges and tropospheric lightning investigations; such findings would be of great value to other disciplines such as power transformers, laser fusion research, and plasma discharge systems. The award would support significant activity in STEM education and student training similar to that recently conducted by the PI and his group. Finally, this award has a strong potential of attracting public attention via local TV and newspaper interviews. The grant awardees indicated also that they would provide the public with excellent public access to the research with frequent open lectures that would generate strong interest by the public in lightning phenomena.The award represents a strong potential for exciting and transformative science. The proposed research would examine in detail fundamental science questions that are related to jet and starter dynamics and their electrical coupling between the lower atmosphere and ionosphere. Moreover, the proposed observational approach is sophisticated providing critical high-time resolution spectral information on the spectral properties of starters and jets that would be studied to produce height profiles of temperature along the path of the conductive path between the top side of the thunderstorm and the lower ionosphere region established by the lightning bolt.

大气区域的耦合、能量学和动力学（CEDAR）计划是一个基础广泛、社区指导的高层大气研究计划，旨在了解从低层大气向上通过电离的高层大气的大气区域的行为。特别令人感兴趣的是存在雷暴等现象的低层大气与100-120公里附近的电离层之间耦合的尺度问题。雷暴事件中闪电现象的物理性质非常复杂，具有高度的时间依赖性，具有表征闪电与电离层耦合的复杂形态，以及相应的电离层下部电离密度的重要时间行为。这些放电是雷暴内部发起的，并植根于主要雷云电荷层之一。该奖项将研究特定瞬态闪电结构的物理过程，这些闪电结构被称为蓝色启动器、射流和巨型射流，它们是雷暴产生的向上放电，分别终止于20-30公里、40-50公里和70-90公里的高度。这些都是雷暴在几分之一秒内突然产生的。该奖项支持的研究将研究这些瞬态发光事件（TIL）现象的能量学和动力学。通常，初始垂直发展速度为~100 km/s，但在100-300 ms后，向上的放电导致巨大的射流突然加速到达电离层下部，速度大于1000 km/s。这项资助的研究将主要用于观测，包括建造一个高速（每秒5000帧）光谱仪，通过快速获取可见原子和分子光谱来分析喷气机和启动器的能量学，从而允许高速测量闪电沿着风暴和电离层之间的路径发出的红到蓝色的相对强度。对这些光谱的分析将提供闪电电离空气路径内垂直温度分布的时间变化。这些关于温度分布的信息将用于量化闪电这些形态特征形成背后的能量学。该奖项具有变革性研究的潜力，将为瞬态等离子体放电的物理知识和理解提供重大进展，这将被证明对实验室放电和对流层闪电调查的研究是非常有价值和高度重要性的；这些发现对电力变压器、激光聚变研究和等离子体放电系统等其他学科具有重要价值。该奖项将支持STEM教育和学生培训方面的重大活动，类似于PI及其团队最近开展的活动。最后，这个奖项有很大的潜力通过当地的电视和报纸的采访来吸引公众的关注。得奖者亦表示，他们会透过经常的公开讲座，为公众提供接触有关研究的良好途径，让公众对闪电现象产生浓厚的兴趣。该奖项代表了令人兴奋和变革的科学的巨大潜力。提出的研究将详细检查与射流和起动器动力学及其低层大气和电离层之间的电耦合有关的基础科学问题。此外，所提出的观测方法是复杂的，提供了关于启动器和射流的光谱特性的关键高时间分辨率光谱信息，这些信息将被研究，以产生雷暴顶部和由闪电建立的电离层下部区域之间的导电路径沿线的温度高度分布。