本文利用中国地磁子午链台站的资料,对1997—1999年期间发生的25次磁暴,用自然正交分量法(NOC)、相关分析和傅里叶分析三种方法,分3个步骤依次分离出依赖于世界时(UT)的暴时变化(Dst)、依赖于地方时(LT)的太阳静日变化(Sq)和太阳扰日变化(SD).对各种变化时空特征的分析表明:①Dst变化清楚地反映出赤道对称环电流磁扰的空间分布和时间演化特征;②满洲里、北京十三陵和琼中台Sq幅度在多数磁暴主相期间出现极大和极小值,反映了Sq焦点在纬度方向上的移动所产生的地磁效应;③SD变化在主相期间最强,在恢复相期间逐渐减弱;④相关分析和傅里叶分析提供了一种能有效提取Sq和SD变化的方法.
With the data of the geomagnetic meridian observatories in China, 25 geomagnetic storms in the period of 1997 to 1999 have been analyzed by using three kinds of methods which are Natural Orthogonal Components (NOC), Correlation Analysis and Fourier Analysis. Three steps have been done to decompose the storm-time variation (Dst) correlating with the universal time ( UT), the solar daily variation ( Sq ) and the disturbance daily variation ( SD ) depending on the local solar time ( LT). The results show that the spacial distribution and the temporal evolution characteristic of equatorial symmetric ring current are reflected clearly by Dst variation. The amplitude of Sq reached maximum or minimum during most main phases in MZL, BMT and QGZ observatories. It reflects the variation of the geomagnetic field from the motion of the Sq focus with latitude. During main phases, the amplitude of SD was the largest. It decreased slowly during the recovery phase. Correlation Analysis and Fourier Analyses offer a useful way to extract the Sq and SD variations.