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

地球高层大气中发生的各种化学反应产生了几种波长范围很广的辐射。这些在文献中被称为气辉，是造成高纬度壮观极光的原因。卫星上的精密仪器和地面系统被用来监测这些排放，以便调查这些排放的起源区域。远紫外辐射已被用于探测地球热层-电离层系统的遥感技术，特别是通过卫星。这些包括来自OI 135.6 nm和N2 Lyman-Birge-Hopfield（LBH）振动带的贡献。全球尺度翼盘观测使命在远紫外波段~ 132 - 160纳米进行的光谱成像提供了白天温度（TDisk）和O/N2组成的测量。为了能够利用卫星飞行任务更准确地确定地球热层-电离层的组成和温度变化，有必要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。随着地球物理遥感技术的改进和远紫外线（FUV：125.0-250.0 nm）观测导致空间气象方面的重要发现，具有成像能力的紫外线光谱法在实验室和地面观测中发挥着日益重要的作用。科罗拉多大学正在进行的GOLD使命使用OI（135.6 nm）和N2 Lyman-Birge-Hopfield（LBH）波段系统（125-250 nm）的日光紫外观测，这两个波段都是光学禁戒辐射。代理的入射太阳能通量（QEUV）产生的光电子是来自使用这些排放。在日光中，一个独特的签名的O/N2柱密度比来自基于卫星的紫外线观测的OI（135.6 nm）和N2 LBH带系统（125-250 nm）之间的强度比光学禁戒发射。O/N2柱密度比和热层温度测量是使用GOLD等地球轨道卫星了解所有地磁条件下全球范围内电离层和热层组成和动态变化的关键。未能准确测量的排放截面有助于O/N2和QEUV检索系统的不确定性（约30%的O/N2报告）。该提议的独特之处在于，利用设计成考虑级联贡献的装置（即，以消除常见的错误，如墙壁碰撞）。这些测量将改进使用基于卫星的地面FUV测量的热层-电离层参数的推导。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.