A case study of global ULF pulsations using data from space-borne and ground-based magnetometers and a SuperDARN radar

Abstract

On 21—22 January 2005 global ULF pulsations in the Pc5 range were observed in the Earth’s magnetosphere. The event took place during a compact high velocity stream of the solar wind, which produced a moderate magnetospheric storm and was characterised by mainly positive values of the interplanetary magnetic field Bz component and by dense plasma. To study the wave field structure of the ULF oscillations during this event we used magnetometer data from the GOES-10 and GOES-12 geostationary satellites, line of sight velocity data from the Kodiak SuperDARN radar, and magnetic measurements from INTERMAGNET observatories. In order to analyse the wave structure along a magnetic field line, GOES measurements were compared with those of ground stations closest to the GOES magnetic foot prints, while the Kodiak measurements were compared with magnetic field data from two INTERMAGNET stations, College and Shumagin, which were located within the Kodiak field of view or very close to it. The study shows a good correspondence and even coherence for some frequency components between pulsations observed near the top of a field line and at its foot and, to a lesser extent, between Kodiak line of sight velocities and conjugated magnetic measurements.