Specific features of the generation of long-periodic geomagnetic pulsations in the event on June 25, 2008

Abstract

The event of the generation of long-periodic geomagnetic Pc5 pulsations occurring on June 25, 2008 under undisturbed geomagnetic conditions is considered using data from ground-based and satellite observations. Two maxima in the frequency bands 1.9–2.2 and 2.9–3.3 mHz are revealed in the spectra of oscillations in the interplanetary medium, magnetosphere, and on the Earth. Pulsations with frequency 1.9–2.2 mHz were detected in all time sectors from low to high latitudes. The maximum amplitude of the oscillations was recorded in the longitude sector coinciding with position of the ion foreshock region. It is assumed that the event under consideration was caused both by variations of the solar wind dynamic pressure (amplified by the foreshock region) and by the direct penetration of ultra-low-frequency waves from solar wind to the magnetosphere.