Mid-Latitude Thermosphere-Ionosphere Na (TINa) Layers Observed With High-Sensitivity Na Doppler Lidar Over Boulder (40.13 degrees N, 105.24 degrees W) ; Geophysical Research Letters

We report the first lidar observations of regular occurrence of mid-latitude thermosphere-ionosphere Na (TINa) layers over Boulder (40.13 degrees N, 105.24 degrees W), Colorado. Detection of tenuous Na layers (similar to 0.1-1 cm(-3) from 150 to 130 km) was enabled by high-sensitivity Na Doppler lidar. TINa layers occur regularly in various months and years, descending from similar to 125 km after dusk and from similar to 150 km before dawn. The downward-progression phase speeds are similar to 3 m/s above 120 km and similar to 1 m/s below 115 km, consistent with semidiurnal tidal phase speeds. One or more layers sometimes occur across local midnight. Elevated volume mixing ratios above the turning point (similar to 105-110 km) of Na density slope suggest in situ production of the dawn/dusk layers via neutralization of converged Na+ layers. Vertical drift velocity of TINa+ calculated with the Ionospheric Connection Explorer Hough Mode Extension tidal winds shows convergent ion flow phases aligned well with TINa, supporting this formation hypothesis. ; National Science FoundationNational Science Foundation (NSF) [AGS-1452351, AGS-2029162, OPP-1443726]; NSFNational Science Foundation (NSF) [AGS-2033787, OPP-1744828]; AFOSR MURI grant [FA9559-16-1-0364] ; Published version ; The authors sincerely appreciate Weichun Fong and John A. Smith for their significant contributions to the STAR lidar development and receiver improvements. The authors are grateful to Jeffery Forbes for invaluable discussions on tidal winds. The authors offer special thanks to Scott P. Sandberg and Mike Hardesty for their tremendous help in setting up the Table Mountain Lidar Observatory. This work was supported by the National Science Foundation grants AGS-1452351, AGS-2029162, and OPP-1443726. The work of ZHX was supported by NSF grant OPP-1744828. SRZ acknowledges support from AFOSR MURI grant FA9559-16-1-0364 and NSF award AGS-2033787.