A statistical study of geomagnetic field line resonance properties

The propagation of ultra low frequency (ULF) waves, in the frequency range of 1-100 mHz, from the mag- netosphere to the ground where they are usually detected is greatly affected by the Earth´s ionosphere. The ionosphere presents a conducting interface between the magnetosphere and atmosphere. In this work magnetic field measurements observed in the topside ionosphere by low Earth orbiting CHAMP satellite and Hermanus (HER) ground station data set is used to test magnetohydrodynamics (MHD) theoretical predictions. This paper aims to illustrate the effect of the ionospheric currents on the propagation ULF waves in the Earth´s magnetosphere. This is attempted by studying field line resonance (FLR) events observed at Hermanus and by CHAMP satellite on crossing HER latitude.