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Comparison of sporadic sodium layer characteristics observed at different time resolutions
Liu, Y. J.1; Clemesha, B. R.1; Wang, J. H.2; Cheng, X. W.3; 北京8701信箱
Department空间天气学国家重点实验室
Source PublicationANNALES GEOPHYSICAE
2013
Volume31Issue:11Pages:1899-1912
ISSN0992-7689
Language英语
KeywordAtmospheric Composition And Structure Middle Atmosphere Composition And Chemistry
AbstractSporadic sodium (Nas) layers, occurring in roughly the same height range as ionospheric sporadic-E layers, were first detected by lidar some 30 yr ago. Nas layers have a typical thickness of a few hundred meters to a few km, with peak atom concentrations several times that of the background layer. Despite a great deal of excellent work over the past decades, the source of Nas layers is still not altogether clear, partly as a result of our incomplete knowledge of Nas layer characteristics. In this paper we concentrate on some typical case studies chosen from the ~127 h of sporadic sodium layer observations made at a time resolution of 1.5 s at Yanqing (115.97° E, 40.47° N), Beijing, China. This is a much better time resolution than what has been employed in most earlier measurements. The results show that the Nas layer peak heights are dispersed at slightly different although adjacent heights. When averaged over several minutes, as has been the case with most earlier measurements, the height scatter results in an apparent layer thickness of a few km. We conclude, therefore, that these dispersed peaks at different but adjacent heights constitute the 5 min Nas layer. Similar to the observations of sporadic-E-ion (Es) layers and meteor rate, we observe quasi-periodic fluctuations on a timescale on the order of several minutes in the peak height and the peak density of sporadic layers, which is a universal feature but concealed by the lower temporal resolution previously adopted. Spatially localized multiple scatterers and multiple thin layers with similar apparent movement in Nas layers are also found. We discuss the possible formation mechanism by the direct deposition of large swarms of micrometeoroids and demonstrate a typical example of meteor trails evolving into a Nas layer, which suggests that this mechanism might indeed occur.; Sporadic sodium (Na-s) layers, occurring in roughly the same height range as ionospheric sporadic-E layers, were first detected by lidar some 30 yr ago. Nas layers have a typical thickness of a few hundred meters to a few km, with peak atom concentrations several times that of the background layer. Despite a great deal of excellent work over the past decades, the source of Nas layers is still not altogether clear, partly as a result of our incomplete knowledge of Nas layer characteristics. In this paper we concentrate on some typical case studies chosen from the similar to 127 h of sporadic sodium layer observations made at a time resolution of 1.5 s at Yanqing (115.97 degrees E, 40.47 degrees N), Beijing, China. This is a much better time resolution than what has been employed in most earlier measurements. The results show that the Nas layer peak heights are dispersed at slightly different although adjacent heights. When averaged over several minutes, as has been the case with most earlier measurements, the height scatter results in an apparent layer thickness of a few km. We conclude, therefore, that these dispersed peaks at different but adjacent heights constitute the 5 min Nas layer. Similar to the observations of sporadic-E-ion (Es) layers and meteor rate, we observe quasi-periodic fluctuations on a timescale on the order of several minutes in the peak height and the peak density of sporadic layers, which is a universal feature but concealed by the lower temporal resolution previously adopted. Spatially localized multiple scatterers and multiple thin layers with similar apparent movement in Nas layers are also found. We discuss the possible formation mechanism by the direct deposition of large swarms of micrometeoroids and demonstrate a typical example of meteor trails evolving into a Nas layer, which suggests that this mechanism might indeed occur.
Funding Project中国科学院空间科学与应用研究中心
Document Type期刊论文
Identifierhttp://ir.nssc.ac.cn/handle/122/1542
Collection空间科学部
Corresponding Author北京8701信箱
Affiliation1.Inst Nacl Pesquisas Espaciais, BR-12227010 Sao Jose Dos Campos, Brazil
2.Chinese Acad Sci, Natl Space Sci Ctr, Beijing, Peoples R China
3.Chinese Acad Sci, Wuhan Inst Phys & Math, Wuhan, Peoples R China
Recommended Citation
GB/T 7714
Liu, Y. J.,Clemesha, B. R.,Wang, J. H.,et al. Comparison of sporadic sodium layer characteristics observed at different time resolutions[J]. ANNALES GEOPHYSICAE,2013,31(11):1899-1912.
APA Liu, Y. J.,Clemesha, B. R.,Wang, J. H.,Cheng, X. W.,&北京8701信箱.(2013).Comparison of sporadic sodium layer characteristics observed at different time resolutions.ANNALES GEOPHYSICAE,31(11),1899-1912.
MLA Liu, Y. J.,et al."Comparison of sporadic sodium layer characteristics observed at different time resolutions".ANNALES GEOPHYSICAE 31.11(2013):1899-1912.
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