On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions

	On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions
	Liu, Jing; Liu, Libo; Zhao, Biqiang; Lei, Jiuhou; Wan, Weixing
刊名	JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
	2011
卷号	116 页码:A12312
ISSN号	2169-9380
通讯作者	Liu, J (reprint author), Chinese Acad Sci, Inst Geol & Geophys, Beijing Natl Observ Space Environm, Beijing 10029, Peoples R China.
中文摘要	The equatorial mass anomaly (EMA) in the thermosphere and equatorial ionization anomaly (EIA) in the ionosphere are two interesting phenomena in low-equatorial latitude regions. Previous studies have shown that the EMA appears between 1000 and 2000 local time (LT) and its location of trough is aligned with dip equator, indicating the plausible role of the EIA structure in the development of EMA. In this report, we conducted a statistical study of the occurrence of postmidnight EMA and EIA on the basis of the CHAMP in situ measurements during 2002-2008. Our results revealed that clear EMA and EIA structures are sometimes visible in the postmidnight sector (0100-0600 LT) during geomagnetic quiet periods (Kp < 3). The postmidnight EMA is not necessarily accompanied by the EIA signature in both case study and statistics sense being distinct from the daytime situation. In addition, the occurrence rates of postmidnight EMA and EIA display contrasting behavior with respect to their local time, longitudinal and solar activity dependences. The highest occurrence rate for EMA is 8% at around 0300 LT, while the occurrence rate of the EIA decreases gradually from about 30% at around 2300 LT to similar to 5% at 0600 LT. Longitudinal occurrence of postmidnight EIA presents a wave-like pattern; however, no salient feature appears for the longitudinal occurrence of EMA. Postmidnight EMA is more likely to occur at lower solar activity, whereas an opposite trend presents in the EIA. On the basis of above results, our findings imply that a simple EIA-EMA cause-effect relationship does not hold in the postmidnight sector.
英文摘要	The equatorial mass anomaly (EMA) in the thermosphere and equatorial ionization anomaly (EIA) in the ionosphere are two interesting phenomena in low-equatorial latitude regions. Previous studies have shown that the EMA appears between 1000 and 2000 local time (LT) and its location of trough is aligned with dip equator, indicating the plausible role of the EIA structure in the development of EMA. In this report, we conducted a statistical study of the occurrence of postmidnight EMA and EIA on the basis of the CHAMP in situ measurements during 2002-2008. Our results revealed that clear EMA and EIA structures are sometimes visible in the postmidnight sector (0100-0600 LT) during geomagnetic quiet periods (Kp < 3). The postmidnight EMA is not necessarily accompanied by the EIA signature in both case study and statistics sense being distinct from the daytime situation. In addition, the occurrence rates of postmidnight EMA and EIA display contrasting behavior with respect to their local time, longitudinal and solar activity dependences. The highest occurrence rate for EMA is 8% at around 0300 LT, while the occurrence rate of the EIA decreases gradually from about 30% at around 2300 LT to similar to 5% at 0600 LT. Longitudinal occurrence of postmidnight EIA presents a wave-like pattern; however, no salient feature appears for the longitudinal occurrence of EMA. Postmidnight EMA is more likely to occur at lower solar activity, whereas an opposite trend presents in the EIA. On the basis of above results, our findings imply that a simple EIA-EMA cause-effect relationship does not hold in the postmidnight sector.
学科主题	空间物理
收录类别	SCI
资助信息	National Natural Science Foundation of China [40725014, 41074112, 40804041, 41174139]; CMA [GYHY201106011]; Specialized Research Fund for State Key Laboratories
语种	英语
公开日期	2014-12-15
内容类型	期刊论文
源URL	[http://ir.nssc.ac.cn/handle/122/3210]
专题	国家空间科学中心_空间科学部
推荐引用方式 GB/T 7714	Liu, Jing,Liu, Libo,Zhao, Biqiang,et al. On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions[J]. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,2011,116:A12312.
APA	Liu, Jing,Liu, Libo,Zhao, Biqiang,Lei, Jiuhou,&Wan, Weixing.(2011).On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions.JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS,116,A12312.
MLA	Liu, Jing,et al."On the relationship between the postmidnight thermospheric equatorial mass anomaly and equatorial ionization anomaly under geomagnetic quiet conditions".JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS 116(2011):A12312.