Case study on total electron content enhancements at low latitudes during low geomagnetic activities before the storms
会议名称：《中国科学院地质与地球物理研究所2008学术年会》
会议日期：2009年
学科分类：070802[理学-空间物理学] 07[理学] 0708[理学-地球物理学]
基 金：supposed by National Natural Science Foundation of China(40725014,40674090,40134020) National Important Basic Research Project(2006CB806306)
关 键 词：Ionosphere(Equatorial ionosphere Ionosphereatmosphere interactions Ionospheric disturbances)
摘 要：Sometimes the ionospheric total electron content (TEC) is significantly enhanced during low geomagnetic activities before *** this article,we investigate the characteristics of those interesting TEC enhancements using regional and global TEC *** analyzed the low-latitude TEC enhancement events that occurred around longitude 120°E on 10 February 2004,21 January 2004, and 4 March 2001,*** TEC data are derived from regional Global Positioning System(GPS) observations in the Asia/Australia sector as well as global ionospheric maps(GIMs) produced by Jet Propulsion Laboratory(JPL). Strong enhancements under low geomagnetic activity before the storms are simultaneously presented at low latitudes in the Asia/Australia sector in regional TEC and JPL GIMs. These TEC enhancements are shown to be regional events with longitudinal and latitudinal *** regions of TEC enhancements during these events are confined at narrow longitude ranges around longitude 120°*** latitudinal belts of maxima of enhancements locate around the northern and southern equatorial ionization anomaly(EIA) crests,which are consistent with those low-latitude events presented by Liu et al.(2008).During the 4 March 2001 event,the total plasma density N observed by the Defense Meteorological Satellite Program(DMSP) spacecraft F13 at 840 km altitude are of considerably higher values on 4 March than on the previous day in the TEC enhanced *** TEC enhancement events are possibly due to contributions from auroral/magnetospheric origins;while there are also quasiperiodic enhancement events not related to geomagnetic activity and associated probably with planetary wave type oscillations (*** 6 January 1998 event).Further investigation is warrented to identify/separate contributions from possible sources.