【摘要】 以河北省昌黎地震台为例,使用该台地磁Z分量的分钟值数据,分别对比了正常时段、磁暴发生时段、低点位移时段的主要频率谱值变化特征.通过多频点功率谱对数拟合,发现在数据长度相等的情况下,相对于正常时段而言磁暴时段各频率的能量明显增强,特别是高频端尤其明显;而当大范围低点位移发生时,高频端的能量基本与正常时段持平,但4个小时以上的周期功率谱大部分要低于正常段.通过对多日低点位移时段的FFT累加与正常时段对比后发现,低点位移发生时,8.5小时和13.7小时周期的频谱值增加.通过与DE-METER卫星观测的电子密度数据空间图象进行对比,发现地磁低点位移的发生与空间Ne的增加有很好的对应性.最后对这些变化特征及低点位移可能产生的机制进行了探讨.更多还原

【Abstract】 As an example, this paper analyzed Z component of the geomagnetic record at Changli station in Hebei province, to investigate the low point displacement characteristics. The minute data of geomagnetic Z component was used to analyze the spectral values of its main frequency components during normal time, geomagnetic storm time and low point displacement time, respectively. After fitting ten high spectral values with a logarithmic function, it is found that, with the same length of data, the spectral values at geomagnetic storm time increase apparently as compared with those at normal time, especially at high frequency part. When low point displacement occurred, the spectral values at high frequency approximate to those at normal time, but spectral values at periods above 4 hours are mostly lower than those at normal time. By accumulating some FFT results at low point displacement and normal time, it is shown that, spectral values at periods of 8.5 and 13.7 hour increase at low point displacement time relative to those at normal time. By comparing our result with the images of Ne observed at DEMETER satellite, we found that the occurrence of geomagnetic low point displacement well corresponds to the increase of Ne in ionosphere. Finally we discussed these spectral features and the mechanism of geomagnetic low point displacement.更多还原