Comparison of sporadic sodium layer characteristics observed at different time resolutions

	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
刊名	ANNALES GEOPHYSICAE
	2013
卷号	31 期号:11 页码:1899-1912
关键词	Atmospheric composition and structure middle atmosphere composition and chemistry
ISSN号	0992-7689
通讯作者	北京8701信箱
中文摘要	Sporadic 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.
英文摘要	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.
学科主题	空间物理
语种	英语
内容类型	期刊论文
源URL	[http://ir.cssar.ac.cn/handle/122/1542]
专题	国家空间科学中心_空间科学部
作者单位	1.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
推荐引用方式 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..(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.