Intensity of Pc5 Geomagnetic Pulsations Observed on the Earth's Surface, Depending on the Corresponding Oscillation Mode (Poloidal or Toroidal) in the Magnetosphere

Thirty-six cases of Pc5 geomagnetic pulsations on the GOES-8 geostationary satellite for 2001, which had amplitudes equal to several nanoteslas and continued for more than an hour, have been studied. Twenty-two and 14 pulsations were toroidal and poloidal, respectively. All these pulsations were compared with geomagnetic observations at the Poste-de-la-Baleine observatory (PBQ), which was located near the satellite projection. It was established that the pulsation frequencies on the ground and in the magnetosphere do not always coincide. It has been detected that poloidal oscillations have small and large amplitudes on the ground and in the magnetosphere, respectively; the situation is opposite for toroidal oscillations. The amplitude of ground-level pulsations to a larger degree depends on the azimuthal field component in the magnetosphere than on the radial component.