Spectral features of geomagnetic low　point displacement and its mechanism

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 illuslxated 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