Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes

doi:10.1029/2007JA012283

	Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes
	Liu, Libo ; Zhao, Biqiang ; Wan, Weixing ; Venkartraman, S.; Zhang, Man-Lian ; Yue, X.
刊名	JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
	2007-07-13
卷号	112 期号:A7
ISSN号	2169-9380
DOI	10.1029/2007JA012283
文献子类	Article
英文摘要	In this paper, the 10-year (1996-2005) measurements of total ion density (N-i) from the Defense Meteorological Satellite Program ( DMSP) spacecraft at 0930 and 2130 LT have been analyzed to investigate the yearly variations of global plasma densities in the topside ionosphere at magnetic latitudes from 60 degrees S to 60 degrees N. Results indicate that there are strong yearly variations in the DMSP Ni at 840 km. The annual components of longitude-averaged N-i dominate at most latitudes with maxima around the June solstices in the Northern Hemisphere and the December solstice in the Southern Hemisphere. In contrast, seasonal anomaly ( maxima Ni around the December solstice) exists in the northern equatorial zone. Moreover, the differences in N-i at the two solstices are not symmetrical about the magnetic equator, being generally higher in the Southern Hemisphere than in the Northern Hemisphere. Conjugate-averaged N-i is substantially greater at the December solstice than at the June solstice. This annual asymmetry is modulated by solar activity effect and has latitudinal and longitudinal structures. The longitude effects of the annual asymmetry depend on local time, being stronger in the evening sector than in the morning sector. The solstice differences and annual asymmetry are more marked with increasing solar activity. The annual asymmetry appears not only in the rising phase of the solar cycle but also in the declining phase. Thus the solar condition differences between the two solstices do not account for the N-i asymmetry. The concentration of neutral oxygen [O], provided from the NRLMSIS model, shows a similar pattern of annual and hemispheric asymmetries. Moreover, effects of the HWM model neutral winds are also constituent with the change patterns of N-i. Therefore, considering the principal processes in the topside ionosphere, the changes of [O] and the rates of thermospheric winds should contribute to the annual asymmetry in N-i at 840-km altitude.
WOS关键词	SOLAR-ACTIVITY VARIATIONS ; F-REGION ; SEMIANNUAL VARIATIONS ; ELECTRON-DENSITY ; ION DENSITY ; F2-LAYER ; ASYMMETRY ; MAXIMUM ; MODEL ; WINDS
WOS研究方向	Astronomy & Astrophysics
语种	英语
出版者	AMER GEOPHYSICAL UNION
WOS记录号	WOS:000248036600001
内容类型	期刊论文
源URL	[http://ir.iggcas.ac.cn/handle/132A11/67504]
专题	中国科学院地质与地球物理研究所
通讯作者	Liu, Libo
作者单位	1.Chinese Acad Sci, Inst Geol & Geophys, Beijing 100029, Peoples R China 2.Univ Texas, William B Hanson Ctr Space Sci, Richardson, TX USA
推荐引用方式 GB/T 7714	Liu, Libo,Zhao, Biqiang,Wan, Weixing,et al. Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,2007,112(A7).
APA	Liu, Libo,Zhao, Biqiang,Wan, Weixing,Venkartraman, S.,Zhang, Man-Lian,&Yue, X..(2007).Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes.JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,112(A7).
MLA	Liu, Libo,et al."Yearly variations of global plasma densities in the topside ionosphere at middle and low latitudes".JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 112.A7(2007).