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

每天都有大量的宇宙尘埃落在地球上，金属原子和离子通过流星烧蚀和溅射进入上层大气，形成永久的金属层（~ 75-105公里），这已经被人们知道了近一个世纪。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（TIMt）层的存在。2021年在博尔德进行的激光雷达观测首次报道了Na物种（TINa）中TIMt层的规律出现，TINa层几乎每天晚上都在黎明前和黄昏后出现。该项目将使用建模和观测来调查博尔德的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金属离子和原子、等离子体中性耦合和中纬度热层潮汐的理解。加深了解将有助于推进空间天气研究。该奖项将支持参与该项目的研究生和本科生。该团队将通过制作YouTube视频、组织K-12年级的科学实地考察等活动，激发年轻一代的科学意识。该项目将使用观测和建模方法来解决以下关键科学问题：1)在像博尔德这样的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、流星消融和化学在TIMt的形成和演化中起什么作用？2)如何利用TIMt层来帮助描述/验证CTMT和ICON（电离层连接探测器）提供的100-200 km热层间隙区域的潮汐风？3)哪种输运在中纬度地区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影响电场影响TIMt层？采用南极TIFe模式的区域TIMt模式将被修改为北部中纬度地区，以研究博尔德TINa层以及离子传输。该团队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。他们将把黎明前的TINa相位、体积混合比及其变化与各种模型或测量（例如CTMT、ICON、HWM、ICON驱动的TIEGCM和SD-WACCM-X + DART）提供的中性风（潮汐风和平均风）、模型或测量（例如TIEGCM、Millstone Hill测量）提供的中纬度北部电场以及流星输入通量（MIF）进行比较，以帮助解释观测结果。比较结果将指导输入参数的选择，以在项目的后期推动TIMt模型。从这个项目中发展出来的一个新的区域时间运输模式将有助于量化对各种因素的个别贡献的理解。在一个激光雷达观测不断增加的世界里，它将成为一个强大的研究工具。从这个项目中获得的关于区域垂直运输和化学的新知识将有助于未来一般流通模式的发展。该团队还将开展几项主要的外展和多元化活动：招募和培训一名女本科生、制作YouTube视频、进行科学实地考察和发布新闻。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。

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.