NSF Award
2330168
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.<br/><br/>This project will use observations and modeling approach to address the following key science questions:<br/>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?<br/>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?<br/>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?<br/><br/>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.<br/><br/>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.
