Collaborative Research: Determination of Crucial Space Weather Component O/N2 by Laboratory Measurements of O and N2 Absolute Electron-Induced Emission Cross Sections

合作研究：通过实验室测量 O 和 N2 绝对电子感应发射截面来确定关键空间天气成分 O/N2

• 批准号: 0850396
• 负责人: Richard Eastes
• 金额: $ 11.44万
• 依托单位: The University of Central Florida Board of Trustees
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2015-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0850396&HistoricalAwards=false
• 关键词: Collaborative; Research; Determination; Crucial; Space

As remote sensing techniques have been refined and the desire for global imaging has increased, spectroscopic observations of atomic oxygen (O) and molecular nitrogen (N2) in the far ultraviolet (FUV) have assumed an important role. The central objective of this project is to determine accurate (~ 15%) electron-induced emission cross-sections for the most important atomic and molecular emissions used for remote sensing of the O/N2 density ratio in the upper atmosphere. This ratio is a primary tool for observing the large scale changes in thermospheric composition that result from geomagnetic and solar variability. The density ratio of O/N2 during the daytime is determined directly from analysis of the intensity ratio of electron-induced ultraviolet emissions of their long-lived excited states, such as the OI emission at 135.6 nm and those from the N2 Lyman-Birge-Hopfield (LBH) bands. For OI 135.6 nm only one measurement and one theoretical calculation of cross-section, both reported more than 30 years ago, are found in the literature and they differ by a factor of two. For N2 LBH there is only one direct measurement of the emission cross-sections, published more than two decades ago. Subsequent empirical calculations based on aeronomical observations gave LBH cross-sections approximately 1.6 times higher. It was suggested that this difference could be due to either limitations in the experimental techniques used when measuring the emissions from one of the long-lived states or a failure to properly account for the cascade contributions of some of the upper states or both. To best fit remote sensing observations, aeronomy modelers have sometimes adjusted the existing cross-sections by as much as 200%. It is uncertain whether to scale to the cross-section of OI 135.6 nm (decreasing it) or to the cross-section of N2 LBH (increasing it) in order to obtain agreement for O/N2 between observations from the TIMED satellite's Global Ultraviolet Imager instrument and the empirical MSIS (Mass-Spectrometer-Incoherent-Scatter) model. As the ratio O/N2 plays a pivotal role in Space Weather studies, accurate absolute emission cross-sections of OI and LBH are important. The project will therefore undertake two tasks: (1) To simultaneously measure the absolute cross-sections of both the OI 135.6 and N2 LBH emissions using the same state-of-the-art experimental facilities at the Laboratory for Atmospheric and Space Physics (LASP) of University of Colorado at Boulder (CU) and the Jet Propulsion Laboratory (JPL); and (2) To use the new cross-sections in an analysis to be performed at the Florida Space Institute (FSI in collaboration with Computational Physics Inc. (CPI), in order to improve use and understanding of OI 135.6 nm and N2 LBH observations. The broader impacts of the project include the provision of high-accuracy cross-sections to the community; the cross sections will enable improved understanding of Earth's atmosphere as well as other oxygen- and N2-bearing planetary atmospheres. Students will participate in the research activities which focus on UV spectroscopy, an important remote sensing technique used by the Earth-orbiting Great Observatories.

随着遥感技术的完善并增加了全局成像的渴望，因此在远紫外线（FUV）中对原子氧（O）和分子氮（N2）的光谱观察结果都承担了重要作用。 该项目的核心目的是确定最重要的原子和分子排放的准确（〜15％）电子诱导的发射横截面，用于遥感在上层大气中的O/N2密度比。 该比率是观察由地磁和太阳可变性导致热层组成的大规模变化的主要工具。 白天O/N2的密度比由对其长寿命激发态的电子诱导的紫外线排放的强度比分析直接确定，例如135.6 nm的OI发射和N2 Lyman-Birge-霍普菲尔德（LBH）乐队。 对于OI 135.6 nm，在文献中发现了30多年前报告的横截面的一个测量和一个理论计算，它们都在文献中发现，它们的差异为两个。 对于N2 LBH，仅在二十多年前发布了发射横截面的直接测量。 随后基于空气观测值的经验计算，LBH横截面高约1.6倍。 有人提出，这种差异可能是由于测量长期寿命之一的排放量或未能正确解释某些上州或两者兼有的级联贡献时所使用的实验技术的局限性。 为了最适合遥感观察，气管建模者有时将现有的横截面调整多达200％。 尚不确定是缩放到OI 135.6 nm（减少它）还是N2 LBH（增加IT）的横截面以获得O/N2的横截面仪器和经验MSI（质谱仪 - 奇异师）模型。由于O/N2的比率在太空天气研究中起关键作用，因此OI和LBH的准确绝对发射横截面很重要。 因此，该项目将承担两项任务：（1）同时使用相同的大气和太空物理实验室（LASP实验室）使用相同的最先进的实验设施来测量OI 135.6和N2 LBH排放的绝对横截面（LASP（LASP）科罗拉多大学博尔德分校（CU）和喷气推进实验室（JPL）； （2）在佛罗里达太空研究所（FSI）与Computational Physics Inc.（CPI）合作进行分析中使用新的横截面，以提高对OI 135.6 NM和N2 LBH观察的使用和理解该项目的更广泛的影响包括向社区提供高级横截面；集中于紫外线光谱的活动，这是一种重要的遥感技术，它是地球孔的大观测器。