Geophysical research: article

Аnnotation: The question is raised about the effect of the orientation of the interplanetary magnetic field (IMF) on the north-southern asymmetry of the occurrence of the Pi1 ultra low frequency (ULF) wave packets in polar caps. The duration of the signals under consideration ranges from several units to tens of minutes, and the frequency lies in the range from tenths of a hertz to several hertz, falling from the leading edge of the signal to the back one. Depending on the IMF vector orientation in the vertical plane, the area of the so-called foreshock is located to the south, or to the north of the geomagnetic equator plane. By analyzing the data of the Antarctic observatory Vostok, it is shown that in the southern polar cap the probability of Pi1 observing is approximately twice higher with the southern orientation of the foreshock than with the northern one. The result indicates that at least an appreciable part of the Pi1 wave packets penetrates into the magnetosphere from the interplanetary medium.