Eine Analyse quasiperiodischer Variationen des Magnetfeldes während geomagnetischer Stürme

Summary

Geomagnetic storms of middle intensity—the so-called moderate storms—are characterized in middle latitudes by fluctuations of pulsation and bay type in all three componentsD, H andZ, the periods of which are within the range of 20 to 120 minutes. They are appearing in all three storm phases (initial, main and recovery phase), generally showing a maximum in the main phase. By the aid of statistic frequency analysis as well as of the calculation of the autocorrelation function and power spectra the fluctuations of this period ranges were analysed for 22 geomagnetic storms of middle intensity during the period of 1952 to 1962, recorded at the Niemegk observatory. In order to get an impression about the dependence on latitude 7 parallel records from a station in higher latitude (Dombas, Norway) were analysed in the same way. Power spectra show that there are favoured some periodicities within the period range of 20 to 120 minutes, especially near 50 to 60 and 90 to 120 minutes. This applies to the investigatedX(H)- andY(D)-components as well in middle as in northern latitudes.