Collaborative Research: Laboratory Measurements of Oxygen (O) and Nitrogen (N2) Ultraviolet (UV) Cross Sections by Particle Impact for Remote Sensing of Thermosphere O/N2 Variation

合作研究：通过粒子撞击实验室测量氧气 (O) 和氮气 (N2) 紫外线 (UV) 截面，以遥感热层 O/N2 变化

• 批准号: 2334618
• 负责人: Joseph Ajello
• 金额: $ 82.57万
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-01-01 至 2026-12-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2334618&HistoricalAwards=false
• 关键词: Collaborative; Research; Laboratory; Measurements; Oxygen

A variety of chemical reactions occurring in the Earth’s upper atmosphere generate several emissions spanning a wide range of wavelengths. These are referred to as airglow in the literature and are responsible for the spectacular aurora at higher latitudes. Sophisticated instruments on-board satellites and ground-based systems have been used to monitor these emissions for investigating the regions where these emissions originate. Far ultraviolet emissions (FUV) have been used in remote sensing techniques for probing Earth’s thermosphere-ionosphere system, especially by satellites. These include contributions from OI 135.6 nm and N2 Lyman-Birge-Hopfield (LBH) vibrational bands. Spectral imaging in the FUV bands ~ 132 – 160 nm by the Global-Scale Observations of the Limb and Disk (GOLD) mission provides daytime measurements of temperature (TDisk) and composition of O/N2. To enable a more accurate determination of composition and temperature changes of Earth’s thermosphere-ionosphere using satellite-based missions, an accurate determination of the emission cross-sections and their radiative lifetime are necessary. The primary goal for this program is to determine the UV emission cross sections needed to accurately model remote sensing observations of the Earth’s dayglow. As Geophysical remote sensing techniques have improved and observations of the far ultraviolet (FUV: 125.0–250.0 nm) have led to important discoveries in Space Weather, UV spectroscopy methods with imaging capability have assumed an increasingly important role in both the laboratory and Terrestrial observations. The ongoing GOLD mission built at the University of Colorado (CU) uses the dayglow UV observations of the OI (135.6 nm) and N2 Lyman-Birge-Hopfield (LBH) band system (125-250 nm), both optically forbidden emissions. The proxy for the incident solar flux (QEUV) producing photoelectrons is derived using these emissions. In the dayglow, a unique signature of the O/N2 column density ratio are derived from satellite-based UV observations of the intensity ratio between the OI (135.6 nm) and N2 LBH band system (125-250 nm) both optically forbidden emissions. The O/N2 column density ratio and thermosphere temperature measurements are keys to understanding ionosphere and thermosphere composition and dynamical changes on a global scale under all geomagnetic conditions using Earth-orbiting satellites like GOLD. The failure to accurately measure the emission cross section contributes to the systematic uncertainty for O/N2 and QEUV retrievals (~ 30% reported for O/N2). The uniqueness of this proposal is the measurement of both the atomic O and molecular N2 absolute Qem (total emission cross section) and Qcasc (cascade-induced cross section) more accurately with an apparatus designed to account for cascade contributions (i.e., to eliminate common errors like wall collisions). These measurements will improve derivation of thermosphere-ionospheric parameters using satellite based terrestrial FUV measurements.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.

地球高层大气中发生的各种化学反应会产生多种波长范围的辐射，这些辐射在文献中被称为气辉，是高纬度地区卫星和地面上的精密仪器产生的壮观极光的原因。远紫外线发射（FUV）已用于探测地球热层-电离层系统的遥感技术，特别是通过卫星。包括来自 OI 135.6 nm 和 N2 Lyman-Birge-Hopfield (LBH) 振动波段的贡献，全球尺度肢体和椎间盘观测 (GOLD) 任务在 FUV 波段 ~ 132 – 160 nm 中进行光谱成像，提供白天的温度测量。 (TDisk) 和 O/N2 成分，以便利用卫星更准确地确定地球热层-电离层的成分和温度变化。在执行任务时，必须准确确定发射截面及其辐射寿命，该计划的主要目标是确定准确模拟地球日光遥感观测所需的紫外线发射截面。远紫外线（FUV：125.0–250.0 nm）的改进和观测导致了空间天气领域的重要发现，具有成像能力的紫外光谱方法在实验室和陆地天气中发挥着越来越重要的作用。科罗拉多大学 (CU) 正在进行的 GOLD 任务使用 OI (135.6 nm) 和 N2 Lyman-Birge-Hopfield (LBH) 波段系统 (125-250 nm) 的日光紫外观测，这两种波段都是光学禁止发射的。产生光电子的入射太阳通量 (QEUV) 的代理值是使用这些发射得出的。在日光中，O/N2 柱密度比的独特特征是从基于卫星的 UV 中得出的。 OI (135.6 nm) 和 N2 LBH 波段系统 (125-250 nm) 之间的强度比观测均为光学禁发射 O/N2 柱密度比和热层温度测量是了解电离层和热层组成以及动态变化的关键。使用 GOLD 等地球轨道卫星在全球范围内的所有地磁条件下无法准确测量发射截面会导致 O/N2 和 QEUV 的系统不确定性。检索（O/N2 报道约为 30%） 该提案的独特之处在于使用设备更准确地测量原子 O 和分子 N2 绝对 Qem（总发射截面）和 Qcasc（级联诱导截面）。旨在考虑级联贡献（即消除壁碰撞等常见错误）。这些测量将改进使用基于卫星的地面 FUV 测量对热层-电离层参数的推导。授予 NSF 的法定使命，并通过评估反映使用基金会的智力优点和更广泛的影响审查标准，被认为值得支持。