CEDAR: Evaluating the Molecular Viscosity Assumption for Gravity Waves in the Upper Thermosphere Using Ground-Based Airglow Observations

该奖项将从实验上确定热层重力波模型中使用的动态分子粘度量的适当表达式。该方法分析了多种地基观测的光学发射、重力波和高层大气发射模式的结果。光学仪器包括4台全天成像仪（ASI）、3台法布里-珀罗干涉仪（FPI）和3台窄视场光度计，全部位于波多黎各的阿雷西博天文台（AO）和库莱布拉远程光学设施（ROF）。位于波多黎各的电离层探空仪所作的电离层观测也将包括在内。将对OI 6300Å和OI 8446Å的排放进行观测，它们都是在上层热层产生的，在黄昏和夜间，OI 8446Å的峰值通常比OI 6300Å高出20-70公里。两条发射线的峰值高度将通过对来自两个地面站点的ASI图像应用三角测量来确定。fpi将提供地面站点上方的扰动垂直风速。ASIs将提供水平重力波相位结构。引力波周期将从所有三种光学发射观测中获得。重力波模拟所需的背景温度和水平风，将由FPI观测得到。扰动垂直速度波场的振幅将借助包括分子粘度和热扩散在内的全波、完全可压缩重力波模型和光电子/光子输运和光发射模型来确定。将垂直速度波场从6300Å峰值高度到8446Å峰值高度的相位和振幅变化与重力波模型对一系列不同动态分子粘度参数值的预测进行比较，以确定最适合观测值的值。这项研究的预期结果是解决Vadas和Crowley提出的一个悬而未决的问题，即动态分子粘度的标准公式是否在上层热层中给出了太大的值。AO的8446Å FPI将通过更换探测器而得到改善，AO和RFO的实验室将增加两个ASIs。这项研究将被整合到阿雷西博天文台的科学、技术、工程和数学（STEM）推广和教育项目中。将制作一张大型海报，以外行的方式描述这项工作，为AO安吉尔拉莫斯基金会游客中心的游客描述这项研究。克尔博士每次进行观察旅行访问时，将在该设施举行一次公开演讲。AO的游客中心每年接待超过10万名游客，其中大多数是参加正规和非正规教育项目的西班牙裔K-12学生。对低至中纬度f区热层中重力波传播的改进建模将导致对电离层不规则触发的更好理解。这些不规则现象引起无线电频率闪烁和通信和导航系统的中断。通过将观测和建模的新结合应用于有关上层热层粘度的开放问题，重力波建模和高层大气物理学领域的知识状况将得到推进。背景风和温度需要作为引力波模型的输入，将由FPI观测提供。重力波在上层热层从一个高度传播和消散时观测到的相位和振幅变化将与模式预测进行比较。这些观测结果的结合将在很大程度上消除对引力波观测研究中通常存在的简化假设的需要，从而有可能回答上述关于上层热层粘度的开放性问题。该奖项反映了美国国家科学基金会的法定使命，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。

This award would determine experimentally what the proper expression should be for the quantity of dynamic molecular viscosity that is used in thermospheric gravity-wave models. The approach is to analyze multiple types of ground-based observations of optical emissions and gravity-wave and upper-atmospheric emission model results. The optical instruments include four all-sky imagers (ASI), three Fabry-Perot interferometers (FPI), and three narrow field-of-view photometers, all located at Arecibo Observatory (AO) and the Culebra Remote Optical Facility (ROF) in Puerto Rico. Ionospheric observations made by an ionosonde located in Puerto Rico are also to be included. Observations would be made of OI 6300Å and OI 8446Å emissions, both of which are produced in the upper thermosphere, with the peak of OI 8446Å typically 20-70 km above that of OI 6300Å during twilight and nighttime hours. Peak heights for the two emission lines would be determined by applying triangulation to the ASI images from the two ground sites. The FPIs would provide perturbation vertical wind velocities above the ground sites. The ASIs would provide horizontal gravity-wave phase structure. Gravity-wave periods will be obtained from all three types of optical emission observations. Background temperature and horizontal wind, required for gravity-wave modeling, would be obtained from FPI observations. The amplitudes of the perturbation vertical velocity wave fields would be determined with the help of a full-wave, fully compressible gravity-wave model including molecular viscosity and thermal diffusion and a photoelectron/photon transport and optical emissions model. The changes in phase and amplitude of the vertical velocity wave fields going from the 6300Å peak altitude to the 8446Å peak altitude would be compared with gravity-wave model predictions for a range of different dynamic molecular viscosity parameter values to determine the value that best fits the observations. The expected outcome of this research is to resolve an open question raised by Vadas and Crowley as to whether the standard formula for dynamic molecular viscosity gives values that are too large in the upper thermosphere. The 8446Å FPI at AO would be improved by detector replacement and two ASIs would be added to the labs at AO and the RFO. This research would be integrated into the Science Technical Engineering and Math (STEM) outreach and educational programs at Arecibo Observatory. A large poster describing the work in layman’s terms would be created to describe the research for visitors to the Angel Ramos Foundation Visitor Center at AO. A public lecture would be provided at that facility during each observing travel visit by Dr. Kerr. The Visitor Center at AO has had more than 100,000 visitors annually, mostly Hispanic K-12 students in formal and informal education programs. Improved modeling of gravity wave propagation in the low to mid-latitude F-region thermosphere will lead to an improved understanding of ionospheric irregularity triggering. These irregularities cause radio frequency scintillations and disruptions of communication and navigation systemThe state of knowledge in the areas of gravity-wave modeling and upper atmospheric physics would be advanced through the application of a novel combination of observations and modeling to an open question about viscosity in the upper thermosphere. Background wind and temperature, needed as inputs to gravity-wave models, will be provided by FPI observations. Observed changes in both phase and amplitude as gravity waves propagate and dissipate going from one altitude to another in the upper thermosphere will be compared with model predictions. The combination of observations will largely eliminate the need for simplifying assumptions typically present in observational gravity-wave studies, making it possible to answer the above-mentioned open question about viscosity in the upper thermosphere.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.