极区电离层在磁坐标系下的世界时变化特征研究

THE CHARACTERISTICS OF THE POLAR IONOSPHERE IN THE GEOMAGNETIC COORDINATES SYSTEM

利用太阳活动低年2007—2010共计4年的COSMIC(Constellation Observing System for Meteorology,Ionosphere,and Climate satellite)掩星观测数据,在修正地磁纬度-磁地方时标系下(地磁坐标系),计算了极区电离层平均电子含量(mPEC)表征极区电离层的世界时(UT)变化特征。结果表明地磁坐标系下南北极区电离层UT变化特征明显,主要是由于极区的太阳光致电离区域随UT变化所致。以mPEC表征的极区电离层电子密度UT变化规律呈正余弦型,在南北极约有12小时的相位差;南极的UT变化强度要大于北极,约是北极的2~3倍,这些特征主要归因于地理轴与地磁轴的夹角在南极大于北极。通过与地理纬度-地方时坐标系下mPEC的UT变化特征对比,发现地磁坐标系下的UT变化强度更大,原因是地磁坐标系下极区电离层的UT变化是太阳光致电离叠加水平输运调制共同作用的结果,而地理坐标系下极区电离层UT变化主要由水平输运产生。

The mean Polar Electron Content(mPEC)over the low solar activity years 2007–2010 in Corrected Geomagnetic Latitude and Magnetic Local Time Coordinates(CGLMLT)is calculated to investigate the Universal Time(UT)variations of the polar ionosphere based on the observation of Constellation Observing System for Meteorology,Ionosphere,and Climate satellite(COSMIC).The results show clear UT variations on mPEC both in the Arctic and Antarctic when seen in the geomagnetic coordinate system.The UT variation of the mPEC changed in a sinusoidal way,with the phase difference about 12 hours between the Arctic and Antarctica.In addition,the UT variation is about 2~3 times larger in the Antarctic than in the Arctic.These features should result from the separation between the geographic pole and the geomagnetic pole.Actually in geographic coordinate system,the UT variation of the mPEC is rather small.The reason should be that the UT variations of mPEC come from solar radiation as well as horizontal transportation in geomagnetic coordinates but only horizontal transportation in geographic coordinate systems.