Spectral features of geomagnetic low point displacement and its mechanism  

作　　者：张学民[1] 钱家栋[1] 王亚丽[2] 赵旭[2] 欧阳新艳[1] 赵庶凡[1] 

机构地区：[1]中国地震局地震预测研究所,中国北京100036 [2]中国地震台网中心,中国北京100036

出　　处：《地震学报》2008年第5期474-483,共10页Acta Seismologica Sinica

基　　金：National Science and Technology Program (2006BAC011302-04-02);Basic Research Project in Institute of Earthquake Science,China Earthquake Administration.

摘　　要：In this paper,Changli station in Hebei Province was taken as an example,in which the minute data of geomagnetic Z component was used to analyze the spectral values of its main frequencies during normal time,geomagnetic storm time and low point displacement time interval respectively. After fitting of ten high spectral values to loga-rithmic functions,it is found that,by using same length of data,the spectral values at geomagnetic storm time in-crease apparently compared with those at normal time,especially at the high frequency segment. While low point displacement occurred,the spectral values at high frequency are approximate to those at normal time,but at period above 4 hours they are mostly lower than those at normal time. Comparison of accumulating of some FFT results at low point displacement and normal time shows that,spectral values at periods of 8.5 and 13.7 hours increase at low point displacement time relative to those at normal time. Compared with the images of Ne observed at DE-METER satellite,it is illustrated that the occurrence of geomagnetic low point displacement is well corresponding with the increase of Ne in ionosphere. Finally it was discussed about those spectral features and the occurrence mechanism of geomagnetic low point displacement.As an example, this paper analyzed Z component of the geomagnetic record at Changli station in Hehei 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.

关 键 词：地磁Z分量 低点位移 快速傅氏变换 DEMETER卫星 电子密度 

分 类 号：P318.24[天文地球—固体地球物理学]