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

该奖项将通过实验确定热层重力波模型中使用的动态分子粘度的正确表达式。该方法是分析光学发射和重力波和高层大气发射模式结果的多种类型的地基观测。光学仪器包括四个全天空成像仪（ASI）、三个法布里-珀罗干涉仪（FPI）和三个窄视场光度计，全部位于阿雷西博天文台（AO）和波多黎各的库莱布拉远程光学设施（ROF）。还将包括由位于波多黎各的电离层探测仪进行的电离层观测。将对OI 6300和OI 8446的辐射进行观测，这两种辐射都是在热层上层产生的，在黄昏和夜间，OI 8446的峰值通常比OI 6300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。ASI将提供水平重力波相位结构。引力波周期将从所有三种类型的光发射观测中获得。重力波模拟所需的背景温度和水平风将从FPI观测中获得。扰动垂直速度波场的振幅将借助于全波、完全可压缩的引力波模型（包括分子粘性和热扩散）以及光电子/光子输运和光发射模型来确定。从6300 ° C峰值高度到8446 ° C峰值高度的垂直速度波场的相位和振幅变化将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，以确定最适合观测的值。这项研究的预期成果是解决一个悬而未决的问题所提出的瓦达斯和克劳利，是否标准公式的动态分子粘度值太大，在上层热层。AO的8446 FPI将通过更换探测器进行改进，AO和RFO的实验室将增加两个ASI。这项研究将被纳入阿雷西博天文台的科学技术工程和数学（STEM）推广和教育计划。一个大海报描述的工作在外行的术语将被创建来描述的研究为游客的天使拉莫斯基金会游客中心在AO。在克尔博士每次考察旅行期间，将在该设施举办一次公开讲座。AO的游客中心每年有超过10万名游客，其中大部分是参加正规和非正规教育项目的西班牙裔K-12学生。改进低中纬度F区热层重力波传播的模型将有助于更好地了解电离层不规则触发。这些不规则现象导致无线电频率振荡和通信及导航系统中断。通过将观测和建模的新组合应用于关于上层热层粘性的未决问题，将提高重力波建模和上层大气物理学领域的知识水平。作为重力波模型输入所需的背景风和温度将由FPI观测提供。将把观测到的重力波在热层上层从一个高度传播到另一个高度时的相位和振幅变化与模型预测进行比较。观测结果的结合将在很大程度上消除简化假设的必要性，通常存在于观测重力波研究中，使其有可能回答上述关于热层上部粘性的开放性问题。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.