CHARACTERISTICS OF GEOMAGNETIC STORM SPECTRA IN MIDDLE AND LOW LATITUDE REGIONS AND THEIR RELATION WITH THE TANGSHAN EARTHQUAKE

In this paper, the characteristics of 80 magnetic storms have been analyzed and compared for the observatories of the seven places: Beijing Qingguang, Changli, Guangzhou, Sheshan, Wuchang and Changchun during 1973-1977.The general natures of the magnetic storm spectral amplitude have been obtained. The results show:1. There are synchronous trends of change in the magnetic storm spectral amplitude for the seven observatories.2. The spectral slopes of all the magnetic storms are almost the same. The yearly average values of the spectral slope b are quite steady within the period range from 0.5 to 6.8 hours. That is, the magnetic storms have the same energy partitioning factor.3. There are significant changes in the yearly average values of spectral intercepts for the three observatories of Beijing, Qingguang and Changli which are near the Tangshan earthquake area, but the yearly average values of the spectral intercepts are quite steady for the four observatories of Guangzhou, Sheshan, Wuchang and Changchun which are far from the Tangshan area. It seems likely that the significant changes are related to the great Tangshan earthquake of July 28, 1976.