First Simultaneous Lidar Observations of Thermosphere‐Ionosphere Fe and Na (TIFe and TINa) Layers at McMurdo (77.84°S, 166.67°E), Antarctica With Concurrent Measurements of Aurora Activity, Enhanced Ionization Layers, and Converging Electric Field

• Published in: Geophysical research letters 2020-10, Vol.47 (20), p.e2020GL090181-n/a
• Main Authors: Chu, Xinzhao, Nishimura, Yukitoshi, Xu, Zhonghua, Yu, Zhibin, Plane, John M. C., Gardner, Chester S., Ogawa, Yasunobu
• Format: Article
• Language: English
• Subjects: Antarctica; Atmospheric Composition and Structure; Atmospheric Processes; aurora; Auroral Ionosphere; Auroral Phenomena; Auroras; Convergence; Electric field; Electric fields; enhanced ionization; Gravity waves; Ion Chemistry and Composition; Ion Chemistry of the Atmosphere; Ionization; Ionosphere; Ionosphere/Atmosphere Interactions; Iron; Lidar; lidar observations; Magnetospheric Physics; Mixing ratio; Natural Hazards; Neutralization; Particle Precipitation; Remote Sensing; Remote Sensing and Disasters; Research Letter; Research Letters; Thermosphere; Thermosphere: Composition and Chemistry; thermosphere‐ionosphere Fe layers; thermosphere‐ionosphere Na layers
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2020GL090181

We report the first simultaneous, common‐volume lidar observations of thermosphere‐ionosphere Fe (TIFe) and Na (TINa) layers in Antarctica. We also report the observational discovery of nearly one‐to‐one correspondence between TIFe and aurora activity, enhanced ionization layers, and converging electric fields. Distinctive TIFe layers have a peak density of ~384 cm−3 and the TIFe mixing ratio peaks around 123 km, ~5 times the mesospheric layer maximum. All evidence shows that Fe+ ion‐neutralization is the major formation mechanism of TIFe layers. The TINa mixing ratio often exhibits a broad peak at TIFe altitudes, providing evidence for in situ production via Na+ neutralization. However, the tenuous TINa layers persist long beyond TIFe disappearance and reveal gravity wave perturbations, suggesting a dynamic background of neutral Na, but not Fe, above 110 km. The striking differences between distinct TIFe and diffuse TINa suggest differential transport between Fe and Na, possibly due to mass separation. Key Points First simultaneous lidar observations show striking differences between distinct TIFe and diffuse TINa, suggesting differential transport We report the observational discovery of the correlation of TIFe with aurora and enhanced ionization, revealing plasma‐neutral coupling All observational evidence points to the Fe+ ion‐neutralization origin of TIFe while suggesting a background of neutral Na above 110 km