CEDAR: Observational and Modeling Studies of Thermosphere-Ionosphere Metal (TIMt) Layers over Boulder

每天都有数吨的宇宙尘埃落在地球上，金属原子和离子通过流星消融和溅射释放到高层大气中，形成了近世纪以来已知的永久金属层（约75-105公里）。2011年在南极洲进行的激光雷达观测揭示了热层-电离层金属层的存在。 2021年，博尔德上空的激光雷达观测首次报告了Na物种（TINa）中TIMt层的定期出现，几乎每晚都在黎明前和黄昏后出现TINa层。 该项目将使用建模和观测来研究博尔德TIMt层，这为研究空间-大气相互作用区域的基本过程打开了一扇新的大门。该项目将大大提高我们对中纬度金属离子和原子、等离子体中性耦合和热层潮汐的理解。 这些认识的提高将有助于推进空间气象研究。该奖项将支持参与该项目的研究生和本科生。该项目将利用观测和模拟的方法来解决以下关键科学问题：1）在博尔德等中纬度地区经常出现的黎明前TINa层的形成机制是什么？中性风、电离层电场、重力、扩散、流星消融和化学作用在TIMt的形成和演化中起什么作用？2)在100-200 km的热层间隙区域，如何使用TIMt层来帮助描绘/验证CTMT和ICON（电离层连接探测器）提供的潮汐风？3)哪种输运在中纬度离子输运中起主要作用--区域输运还是全球输运？等离子体不稳定性是否通过冲击电场影响TIMt层？一个区域TIMt模式，采用从南极洲TIFe模式，将修改为北方中纬度地区研究巨石TINa层以及离子传输。该小组将对激光雷达数据进行深入分析，并最终确定初步观测结果。他们将比较黎明前的TINa相位，体积混合比及其变化与各种模型或测量提供的中性风（潮汐风和平均风）（例如，CTMT、ICON、HWM、ICON驱动的TIEGCM和SD-WACCM-X + DART），以及由模型或测量提供的北方中纬度电场（例如，TIEGCM，Millstone Hill测量），并与流星输入通量（MIF），以帮助解释观测。比较结果将指导输入参数的选择，以驱动TIMt模型在以后几年的项目。 一个新的区域TIMt模型开发的这个项目将有助于量化的理解个人的贡献，从各种因素。它将成为在激光雷达观测不断增加的世界中进行研究的有力工具。从该项目中获得的关于区域垂直输送和化学的新知识将有助于今后发展大气环流模式。该团队还将开展几项主要的外展和多样性活动：招募和培训一名女本科生，YouTube视频，科学实地考察和新闻发布。该奖项反映了NSF的法定使命，并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，被认为值得支持。

With tons of cosmic dust falling on Earth every day, metal atoms and ions are released via meteor ablation and sputtering into the upper atmosphere, forming permanent metal layers (~75–105 km) that have been known for nearly a century. Recent lidar observations in Antarctica in 2011 have revealed the existence of thermosphere-ionosphere metal (TIMt) layers. Regular occurrence of TIMt layers in Na species (TINa) was reported for the first time from lidar observations in 2021 over Boulder, where TINa layers occur before dawn and after dusk nearly every night. This project will use modeling and observations to investigate Boulder TIMt layers that open a new door to study the fundamental processes in the space-atmosphere interaction region. The project will significantly enhance our understanding of metallic ions and atoms, plasma-neutral coupling, and thermospheric tides at mid-latitudes. The enhanced understandings will help advance space weather research. This award will support graduate and undergraduate students involved in this project. The team will conduct outreach activities such as making YouTube videos and organizing science field trips for K-12 to inspire the younger generation in science.This project will use observations and modeling approach to address the following key science questions:1) What are the formation mechanisms for the pre-dawn TINa layers with regular occurrence over midlatitudes like Boulder? What roles do neutral winds, ionospheric electric fields, gravity, diffusion, meteor ablation, and chemistry play in the TIMt formation and evolution?2) How can TIMt layers be used to help delineate/validate tidal winds, provided by CTMT and ICON (Ionospheric Connection Explorer), in the thermospheric gap region of 100-200 km?3) Which transport plays the major role in ion transport at midlatitudes—regional or global transport? Does plasma instability affect TIMt layers via impacting electric fields?A regional TIMt model, adopted from an Antarctica TIFe model, will be modified for the northern midlatitudes to study the Boulder TINa layers as well as ion transport. The team will carry out in-depth analyses of lidar data and finalize the preliminary observational results. They will compare the pre-dawn TINa phases, volume mixing ratios, and their variations with those of neutral winds (tidal winds and mean winds) provided by various models or measurements (e.g., CTMT, ICON, HWM, TIEGCM-driven by ICON, and SD-WACCM-X + DART), with those of electric fields at northern midlatitudes provided by models or measurements (e.g., TIEGCM, Millstone Hill measurements), and with those of meteor input flux (MIF), to help interpret the observations. The comparison results will guide the selection of input parameters to drive the TIMt model in later years of the project. A new regional TIMt model developed from this project will be instrumental in quantifying the understanding of individual contributions from various factors. It will become a powerful tool for studies in a world of ever-increasing lidar observations. The new knowledge gained from this project about the regional & vertical transport and chemistry will assist the future development of general circulation models. The team will also conduct several major outreach and diversity activities: Recruit and train one female undergraduate student, YouTube videos, science field trips, and press releases.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.