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.

Xinzhao Chu,Zhibin Yu,Yasunobu Ogawa,Chester S Gardner,Yukitoshi Nishimura,John M C Plane,Zhonghua Xu

doi:10.1029/2020gl090181

Abstract

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.

Highlights

The metallic atoms and ions in the Earth's upper atmosphere are of extraterrestrial origin as they are produced by the ablation and sputtering of cosmic dust (Plane, 2012)
We report the observational discovery of nearly one‐to‐one correspondence between TIFe and aurora activity, enhanced ionization layers, and converging electric fields
The nearly one‐to‐one correspondence between the TIFe layers and auroral pulses suggests that sputtering of meteoroids is not the source of these high‐altitude TIFe layers since there is no reason for meteoroid sputtering to correlate with

Summary

Introduction

The metallic atoms and ions in the Earth's upper atmosphere are of extraterrestrial origin as they are produced by the ablation and sputtering of cosmic dust (Plane, 2012). We report the first simultaneous, common‐volume lidar observations of TIFe and TINa neutral layers, made with Fe Boltzmann and Na Doppler lidars, over McMurdo (77.84°S, 166.67°E), showing striking differences. Such observations of multiple TIMt species help differentiate their possible sources. Chu and Yu (2017) developed a TIFe model based on this hypothesis which successfully replicated the lidar observations on 28 May 2011 This theory does not rule out other formation mechanisms, for example, direct meteoric deposition via sputtering, and direct transport of neutral metals from their main layers. The concurrent Fe/Na lidar, aurora, ionosonde, and Defense Meteorological Satellite Program (DMSP) observations described here provide an exceptional opportunity to advance TIMt science and reveal complex atmosphere–ionosphere‐magnetosphere coupling processes

Observations With Collocated Fe Boltzmann and Na Doppler Lidars

Findings

Discussion

Conclusions