Temporal and spatial characteristics of Pc1 geomagnetic pulsations

A long-term continuous series (1957–1992) of ground-based observations of ULF emissions in the frequency range of 0.2–5.0 Hz (Pc1) was investigated. To present information uniformly and facilitate comparative analysis, a so-called index N has been introduced, which describes Pc1 activity. Information on cyclic variation of Pc1 activity is given. Pc1 relation to the level of solar and geomagnetic activity, interplanetary magnetic field structure and solar wind parameters (such as the plasma density and bulk velocity, magnetic field strength and direction) in front of the magnetosphere is traced. Latitude dependence of Pc1 activity and its relation to the solar wind conditions are explored.