CEDAR Postdoc: Modeling Studies of Optical Properties of Sprite Streamers and their Chemical Effects on the Upper Atmosphere

CEDAR博士后：雪碧飘带的光学特性及其对高层大气的化学影响的建模研究

• 批准号: 0725360
• 负责人: Ningyu Liu
• 金额: $ 4万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0725360&HistoricalAwards=false
• 关键词: CEDAR; Postdoc; Modeling; Studies; Optical

This project conducts a modeling and observational study to investigate optical properties of sprite streamer discharges and their chemical effects on the upper atmosphere. Sprite discharges represent one of four known types of transient luminous events occurring in the Mesosphere and Lower Thermosphere-Ionosphere (MLTI) regions, which are directly related to the lightning activity in underlying thunderstorms. Although a typical sprite event may occupy a large overall volume of the upper atmosphere, high spatial resolution imagery of sprite events reveals many internal and not yet fully understood small scale features, including bright filamentary channels of ionization. It is quite remarkable that the filamentary structures observed in sprites are the same phenomenon known as streamer discharges at atmospheric pressure, only scaled by reduced air density at higher altitudes. Practical applications of streamers at near ground pressures include ozone production, pollution control and surface processing. However, present knowledge about the chemical effects of sprite streamers on the upper atmosphere is very limited. Driven by lightning discharges during thunderstorms, sprites are one of the manifestations of the upward coupling of electromagnetic energy from tropospheric altitudes to the mesospheric and lower ionospheric regions. In particular, the electrostatic energy provided by lightning discharges in the upper atmosphere is converted into other forms of energy. Some of them obtain sufficient energies to excite, dissociate and ionize neutral molecules in air (N2 and O2). As a result, chemically active species (e.g., atomic N and O) are generated, and they can initiate a chain of reactions leading to production of several important constituents (e.g., NO) in the upper atmosphere. Excited neutral or ionized molecules radiate photons which are subsequently observed by optical imaging instruments as spectacular sprite discharges. The emissions from sprites are a key indicator of electron energetics and the energy conversion process, and the current knowledge about sprites is mostly obtained by analyzing sprite emission data. Intense ionization occurs in sprites as well, which results in the local modification of atmospheric conductivity. Therefore, sprites are an important component within the context of energy budget and chemical composition of the upper atmosphere, and this project addresses the need to characterize and interpret optical properties of sprite streamers and their effects on the upper atmosphere. The specific scientific questions addressed are: (1) What are the chemical effects of sprite streamers on the upper atmosphere? (2) What is the dynamics of optical emissions produced by sprite streamers? The primary result will be better understanding of emissions and chemical effects of sprite streamers, including short and long term effects. The investigation will provide a theoretical basis for a better and more complete analysis of existing and future sprite data (e.g., far-UV and optical data collected by the ISUAL instrument on the FORMOSAT-2 satellite). The broader impacts include collaborations between modelers and experimentalists and the support and further training of a postdoctoral scholar.

该项目进行模拟和观测研究，以调查精灵流光放电的光学特性及其对高层大气的化学影响。 雪碧放电代表了四种已知类型的瞬变发光事件发生在中间层和低热层电离层（MLTI）地区，这是直接相关的闪电活动在底层雷暴。虽然一个典型的精灵事件可能占据了高层大气的很大一部分，但精灵事件的高空间分辨率图像揭示了许多内部的、尚未完全理解的小尺度特征，包括明亮的电离通道。非常值得注意的是，在精灵中观察到的对流结构与大气压下的流光放电相同，只是在更高的高度上减少了空气密度。在近地面压力下，拖缆的实际应用包括臭氧生产、污染控制和表面处理。然而，目前的知识，对上层大气的精灵飘带的化学效应是非常有限的。在雷暴期间由闪电放电驱动，精灵是从对流层高度到中层和低电离层区域的电磁能量向上耦合的表现之一。特别是，高层大气中闪电放电所提供的静电能被转换成其他形式的能量。 它们中的一些获得足够的能量来激发、解离和分解空气中的中性分子（N2和O2）。结果，化学活性物质（例如，原子N和O），并且它们可以引发导致产生几种重要成分的反应链（例如，在高层大气中。激发的中性或电离分子辐射光子，随后被光学成像仪器观察到壮观的精灵放电。精灵的发射是电子能量学和能量转换过程的重要指标，目前对精灵的认识主要是通过分析精灵发射数据来获得的。强烈的电离发生在精灵，以及，这导致在当地修改的大气电导率。因此，精灵是高层大气能量收支和化学组成的一个重要组成部分，本项目解决了需要描述和解释精灵流光的光学特性及其对高层大气的影响。 具体的科学问题是：（1）精灵飘带对高层大气的化学影响是什么？(2)精灵飘带产生的光辐射的动力学是什么？ 主要结果将是更好地了解精灵飘带的排放和化学影响，包括短期和长期影响。该调查将为更好和更完整地分析现有和未来的子画面数据提供理论基础（例如，FORMOSAT-2号卫星上的ISUAL仪器收集的远紫外线和光学数据）。 更广泛的影响包括建模者和实验者之间的合作以及对博士后学者的支持和进一步培训。