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

该合同将通过一个实验室目标来推进紫外线遥感的能力，该目标的中心是确定地球日光遥感观测所需的紫外线发射截面（Qem）。在日光中，基于卫星的紫外线观测得到的O/N2密度比的独特特征，来自于测量OI （135.6 nm (3P2- 5So2)）和N2 Lyman-Birge-Hopfield （LBH）波段（125-250 nm）发射的强度比。这种O/N2密度比是理解所有地磁条件下全球范围内电离层和热层组成变化的关键。然而，这两组光谱跃迁的总发射截面尚未测量。这两个总发射截面中的每一个都是直接激发发射截面和级联截面的总和。叶栅截面约占总截面的30-50%。由于柱密度比O/N2在空间天气研究中起着关键作用，因此准确测量OI和LBH排放的Qem绝对值对于解释热层组成（O/N2）变化的幅度和时间演变至关重要。同样，极光遥感所需的高能质子（H+）和氢原子撞击Qem的实验室测量也不充分。这主要有两个重点。一名研究生（UCF）和一名本科生将在这项工作中得到支持。该奖项项目的第一个目标是使用该团队位于加州理工学院/喷气推进实验室的实验设施，测量125 nm至250 nm之间的LBH波段和135.6 nm的OI （3P2—5So2）的绝对直接电子，H+和H撞击Qem，从它们的发射阈值到500 eV的电子撞击，到50 keV的H+和H原子撞击。该团队还将在科罗拉多大学测量来自这些上游州的瀑布过程。中佛罗里达大学（UCF）和计算物理公司（CPI）的天文学家将使用对美国太空任务至关重要的两种经典粒子传输代码：AURIC和GLOW，对遥感数据进行建模。

This award would advance the capabilities for UV remote sensing by targeting a laboratory goal, which is centered on the determination of the UV emission cross sections (Qem) needed for remote sensing observations of the Earth's dayglow. In the dayglow a unique signature of the O/N2 density ratio, from satellite-based UV observations, comes from measuring the intensity ratio of the OI (135.6 nm (3P2- 5So2)) and N2 Lyman-Birge-Hopfield (LBH) band (125-250 nm) emissions. This O/N2 density ratio is a key to understanding the ionosphere and thermosphere composition changes on a global scale under all geomagnetic conditions. However, the total emission cross sections of these two sets of spectral transitions have not been measured. Each of these two total emission cross sections is a sum of a direct excitation emission cross section and a cascade cross section. The cascade cross sections are about 30-50% of the total cross section. As the column density ratio O/N2 plays a key role in Space Weather studies, accurate absolute measurements of Qem for both OI and LBH emissions are vital for explaining both the magnitude and temporal evolution of thermosphere composition (O/N2) changes. Similarly, the energetic proton (H+) and H atom impact laboratory measurements of Qem needed for auroral remote sensing are inadequate. The main focus of this is two-fold. One graduate student (UCF) and one undergraduate student would be supported in this effort.The first goal of the award project would be to measure the absolute direct electron, H+, and H impact Qem for both the LBH band between 125 nm to 250 nm and OI (3P2--5So2) at 135.6 nm from their emission thresholds to 500 eV by electron-impact, to 50 keV by H+ and H atom impact, using the team's experimental facilities located at Caltech/JPL. The team would also measure at the University of Colorado the cascade processes from these upper states. Aeronomers at the University of Central Florida (UCF) and Computational Physics Inc. (CPI) would model the remote sensing data using two classic particle transport codes that are paramount to the US space mission: AURIC and GLOW.