Collaborative Research: CEDAR--A Novel Technique for Estimating Oxygen Density in the Mid-Latitude Thermosphere

本项目旨在结合现代仪器和最先进的模型，开发一种精确的技术来确定中纬度热层中的原子氧密度。该方法将结合光学和雷达测量来约束一个关键的热层O原子发射的正演模型，即8446 a的暮光气辉，然后使用约束模型来开发一个适用于其他中纬度地区的[O]估计方案。8446 A发射一直被认为是[O]遥感的理想候选者，因为它的发射模型相对简单，该项目将在两个不同的中纬度设施：马萨诸塞州的Millstone Hill （MH）天文台和波多黎各的Arecibo天文台（AO）获得前所未有的8446 A光谱数据，这些数据在各种观测条件下。从嵌套的非相干散射雷达、法布里-珀罗干涉仪和光度计测量中获得的额外参数不仅可以作为额外的正演模型约束，还可以帮助评估当前模型假设的有效性，特别是关于8446 A生产的二次源的作用。与模型参数依赖性的彻底量化一起，约束正演模型将用于开发一种新的反理论技术，以从中纬度测量的8446 a亮度估计热层[O]。中性原子氧是地球200 - 600公里热层的主要成分，其定量分析之所以重要，有几个原因。在该区域，其与f区电离层中的主要离子O+的共振电荷交换在热层和电离层之间的动量和能量交换中起着至关重要的作用。同样，它与H+的电荷交换也一直被认为是电离层和等离子层之间离子传输的重要影响因素。由于这种强烈的化学耦合，许多基本气动计算的准确性——如输运系数的推导、中性风速、能量沉积速率、化学反应速率或光化学发射亮度——取决于[O]的准确规格。因此，目前热层组成和密度的不确定性限制了对热层-电离层耦合系统的理解，无论是在其气候变率方面，还是在其对来自上方和下方的脉冲强迫的响应方面。发展一种新的地面测量热层[O]的能力将有利于国家科学基金会雪松计划的这两个中心优先事项。一名研究生将在该项目的支持下接受航空相关领域的培训。学生将熟悉ISR光谱的采集和分析，以及光学SHS， FPI和光度计数据的采集和分析。可用于本科生研究支持的内部资金，以及AO在本科生研究经验（REU）计划中的强烈参与，也为向本科生介绍航空提供了另一个机会。

This project aims to develop an accurate technique for determining the atomic oxygen density in the mid-latitude thermosphere by combining modern instrumentation with state of the art modeling. The method will combine optical and radar measurements to constrain a forward model of a key thermospheric O-atom emission, the twilight airglow at 8446 A, and in turn use the constrained model to develop an [O] estimation scheme suitable for application at other mid-latitude locations. The 8446 A emission has long been considered an ideal candidate for [O] remote sensing owing to its relatively simple emission model, and the project will acquire an unprecedented set of 8446 A spectral data under various observational conditions at two distinct mid-latitude facilities: Millstone Hill (MH) Observatory in Massachusetts and Arecibo Observatory (AO) in Puerto Rico. Additional parameters derived from nested incoherent scatter radar, Fabry-Perot interferometer, and photometer measurements will not only serve as additional forward model constraints, but also help assess the validity of current model assumptions, specifically with regard to the role of secondary sources of 8446 A production. Together with a thorough quantification of model parameter dependencies, the constrained forward model will be used to develop a novel inverse-theoretical technique to estimate thermospheric [O] from measured 8446 A brightness at mid-latitudes. Quantification of neutral atomic oxygen, the dominant constituent in the Earth's thermosphere between 200 - 600 km, is important for several reasons. In this region, its resonant charge exchange with O+, the principle ion in the F-region ionosphere, plays a vital role in both the momentum and energy exchange between the thermosphere and ionosphere. Similarly, its charge exchange with H+ has long been recognized as an important influence on ion transport between the ionosphere and plasmasphere. Owing to this strong chemical coupling, the accuracy of many fundamental aeronomical calculations -- such as the derivation of transport coefficients, neutral wind speeds, energy deposition rates, chemical reaction rates, or photochemical emission brightnesses -- hinges on accurate specification of [O]. Thus, current uncertainties in thermospheric composition and density limit the understanding of the coupled thermosphere-ionosphere system, both with regard to its climatological variability as well as its response to impulsive forcing from above and below. The development of a new, ground-based capability of measuring thermospheric [O] will benefit both of these central priorities of the NSF CEDAR program. One graduate student will be trained in this Aeronomy-related area with support from the project. The student will gain familiarity with acquisition and analysis of ISR spectra as well as that of optical SHS, FPI, and photometer data. Available internal funds for undergraduate research support, together with the strong involvement of AO in the Research Experiences for Undergraduates (REU) program, presents another opportunity to introduce undergraduate students to aeronomy as well.