Unusual vertical oscillations in sodium density and the formation of sporadic sodium layer over the Zhongshan station

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Published: 2025-09-26
DOI: https://doi.org/10.4401/ag-9289

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Alicreance Hiyadutuje
South African National Space Agency (SANSA), Hermanus, South Africa
Xiangcai Chen
MNR Key Laboratory for Polar Science, Polar Research Institute of China, Shanghai, China; Antarctic Zhongshan Ice and Space Environment National Observation and Research Station, Polar Research Institute of China, Shanghai, China
https://orcid.org/0000-0002-6325-5049
John Bosco Habarulema
South African National Space Agency (SANSA), Hermanus, South Africa; Department of Physics and Electronics, Rhodes University (RU), Makhanda, South Africa; Centre for Space Research, North‑West University (NWU), Potchefstroom , South Africa
https://orcid.org/0000-0002-9716-7688
Michael J. Kosch
South African National Space Agency (SANSA), Hermanus, South Africa, Department of Chemistry and Physics, University of KwaZulu Natal (UKZN), Durban, South Africa, Department of Physics, University of Lancaster (UL), UK
https://orcid.org/0000-0003-2846-3915
Judy A. E. Stephenson
Department of Chemistry and Physics, University of KwaZulu Natal (UKZN), Durban, South Africa
https://orcid.org/0000-0002-3840-7979
Tshimangadzo Merline Matamba
South African National Space Agency (SANSA), Hermanus, South Africa, Department of Physics and Electronics, Rhodes University (RU), Makhanda, South Africa
https://orcid.org/0000-0002-3466-7933
Wentao Huang
MNR Key Laboratory for Polar Science, Polar Research Institute of China (PRIC), Shanghai, China, Antarctic Zhongshan Ice and Space Environment National Observation and Research Station, Polar Research Institute of China (PRIC), Shanghai, China, State Key Laboratory of Lunar and Planetary Sciences, Macau University of Science and Technology (MUST), Macau, China
Chao Ban
State Key Laboratory of Atmospheric Environment and Extreme Meteorology, Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), Beijing, China, Laboratory of Middle Atmosphere and Global Environment Observation, Institute of Atmospheric Physics, Chinese Academy of Sciences (CAS), Beijing, China

Abstract

Unusual vertical oscillations with some wave structures were observed in the sodium (Na) density layers (SLs) in Antarctica on 1 September 2019, by means of the lidar located at Zhongshan (69°S, 76°E). There was a clear vertical convection of the wavy sodium density layers which populated the region at an altitude of between ~90 and ~102 km producing the Sporadic/Sudden Sodium Layers (SSLs).


The vertical oscillations had an average wavelength, average speed and period of ∼3.0‑4.5 km, ∼7.8 m/s and ∼7.3‑8.5 min, respectively. The possible cause of these vertical oscillations, as well as the mechanisms that could be behind the generation of these oscillations and wavy SSLs, were investigated. The Global Positioning System (GPS) satellite receiver located at Davis (68.6°S, 77.9°E), 116 km away from Zhongshan, was used to derive the Total Electron Content (TEC) perturbations in the region surrounding Zhongshan. SuperDARN HF radar at Zhongshan also showed some waves in the first 10 range gates (180‑800 km away), suggesting that the Traveling Ionospheric Disturbances (TIDs) were propagating in the 𝐸‑region. The cross‑correlation between GPS and lidar wave structures was computed. A good to strong correlation of –0.6‑–0.9 was found between waves observed by GPS and lidar. Additionally, a moderate correlation was found between the SuperDARN radar and lidar wave structures. The lidar neutral temperature showed upward Atmospheric Gravity Waves (AGWs), while SuperDARN and GPS showed the downward TIDs. Based on the polar cap (PC) index, TIDs could have been generated by Joule heating due to geomagnetic storm effects in the region. The estimated Richardson number values between 80 and 105 km at 16:00‑24:00 UT suggest that convective and dynamic instabilities could have generated the observed SSLs and AGWs.


Vertical oscillation of the sodium density layers could have taken place because of waves breaking and interference from the downward TIDs and upward AGWs.

Article Details

Issue

Vol. 68 No. 4 (2025)

Section

Atmospheric Sciences
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How to Cite

(1)
Hiyadutuje, A.; Chen, X.; Habarulema, J. B. .; Kosch, M. J. .; Stephenson, J. A. E. .; Matamba, T. M. .; Huang, W.; Ban, C. Unusual Vertical Oscillations in Sodium Density and the Formation of Sporadic Sodium Layer over the Zhongshan Station. Ann. Geophys. 2025, 68 (4), A449. https://doi.org/10.4401/ag-9289.

References