A Novel Faraday Filter-based Spectrometer for Studying the Sodium Airglow and Measuring the Atomic Oxygen Mixing Ratio in the Upper Mesosphere

一种新型法拉第滤光片光谱仪，用于研究钠气辉并测量上层中间层的原子氧混合比

• 批准号: 0804295
• 负责人: Chiao-Yao She
• 金额: $ 10万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-06-01 至 2011-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0804295&HistoricalAwards=false
• 关键词: Novel; Faraday; Filter; based; Spectrometer

This project will develop and deploy a new optical instrument, a compact spectrometer, that will enable new measurements of the mesospheric sodium nightglow. One of the primary aims is to determine the ratio of two sodium emission lines, the D2 and D1. Early studies predicted that the D2/D1 ratio might differ from its quantum statistical value of 2 due to chemical interactions. However, measurements taken three decades ago using a Fabry-Perot instrument reported a value of 1.98±0.1; since then, 2 has taken to be the correct value without further investigation. Recently, T. G. Slanger, J. M. C. Plane and others have searched through sky spectra from Keck telescopes taken over 8 years, and deduced that depending on atmospheric conditions, the value NaRD = I(D2)/I(D1) lies between 1.2 and 1.8. A clear seasonal dependence of this ratio, with higher values in equinox and lower values in solstice, was noted as well. They proposed a modified Chapman mechanism which suggests competing pathways of NaO+O reactions produce Na nightglow emission. Substantiated by laboratory experiments, they concluded that the ratio NaRD is a reliable proxy for the measurement of the [O]/[O2] ratio. Since atomic oxygen is probably the most important species in determining the chemistry and dynamics of the mesosphere and lower thermosphere (MLT), even an indirect real-time determination of [O]/[O2] could greatly advance our understanding of the MLT energy balance, especially since there is no direct ground-based method for observing the atomic oxygen concentration, [O]. Through this project, a novel, compact spectrometer, based on a pair of modified Na vapor Faraday filters, will be designed to measure Na nightglow and to determine NaRD. In addition to NaRD, the method can also determine the pathway fractions of the two possible reactions in the modified Chapman process. The NaRD spectrometer will be deployed at the Colorado State University lidar site for intitial testing and calibration. The project involves a research scientist as Co-PI and a graduate student for his Ph.D thesis. The research would lead to the development of an inexpensive compact spectrometer that could be used at other observatories with a simple sodium lidar. The project will contribute to studies of atomic oxygen in the mesopause region as more data are gathered from various sites in the future. Such measurements will improve the understanding of the aeronomy of airglow processes, most of which involve interactions with O.

该项目将开发和部署一种新的光学仪器-小型光谱仪，从而能够对中间层钠夜辉进行新的测量。 主要目的之一是确定两条钠发射线D2和D1的比率。 早期的研究预测，由于化学相互作用，D2/D1比值可能与其量子统计值2不同。然而，三十年前使用法布里-珀罗仪器进行的测量报告的值为1.98±0.1;从那时起，2被认为是正确的值，没有进一步的研究。最近，T. G.斯兰格，J.M. C.普兰和其他科学家研究了凯克望远镜8年来拍摄的天空光谱，并推断根据大气条件，NaRD = I（D2）/I（D1）的值在1.2和1.8之间。一个明确的季节依赖性的这一比例，较高的值在春分和较低的值在冬至，以及注意到。他们提出了一种修正的查普曼机制，该机制表明NaO+O反应的竞争途径产生Na夜光发射。 通过实验室实验证实，他们得出结论，NaRD比率是测量[O]/[O2]比率的可靠替代物。 由于原子氧可能是决定中间层和低热层（MLT）的化学和动力学的最重要的物种，即使是间接实时测定[O]/[O2]也可以大大提高我们对MLT能量平衡的理解，特别是因为没有直接的地面方法来观测原子氧浓度[O]。 通过本项目，将设计一种基于一对改进的钠蒸气法拉第滤光片的新型紧凑型光谱仪，用于测量钠夜辉和测定NaRD。除NaRD外，该方法还可以测定改进的Chapman过程中两个可能反应的途径分数。 NaRD光谱仪将部署在科罗拉多州立大学激光雷达站点进行初始测试和校准。 该项目涉及一名研究科学家作为合作PI和一名研究生为他的博士论文。 这项研究将导致开发一种廉价的紧凑型光谱仪，可用于其他天文台的简单钠激光雷达。 随着今后从各个地点收集到更多的数据，该项目将有助于中层顶区域原子氧的研究。 这些测量将提高对气辉过程的高层大气学的理解，其中大部分涉及与O的相互作用。