THE GEOMAGNETIC DISTURBANCES CAUSED BY SOLAR ACTIVITY IN MARCH 1991
Gao Yu-fen(Institute of Geophysics State Seismological Bureau,Bejiing 100081)Zhang Gong-liang(Center for Space Science and Applied Research,Academia Sinica,Beijing)Zhou Rong-mao(Institute of Geophysics,State Seismological Bureau,Beijing)
Using the geomagnetic data of Baijiatuan and Madaoyu observatories in Beijing,the magnetic storms of March 24-27 caused by solar activity during the last ten days of March 1991 are analysed. From the records of mid-latitude, one could find the storms have some specific morphological features: the amplitude of the sudden commencement is very large, the most severe activity of the storms is produced by the substorm beginning immediately after the sudden commencement; there appear some pulsations in many intervals during the storms, in particular, the pulsations with T = 650s are outstanding.It is polarization direction displays mainly left-handed,but,it mixed up with right-handed ones without any obvious regularities. The results of spectra analysis indicate that power spectrum p(f) of the whole storm follows the form P(f) = f-2.0. In addition, the interplantary disturbances are discussed,which may cause the storms.