Pc 3-4 ulf magnetic variations measured in the ionosphere by eiscat

ULF pulsations of Pc 3-4 type were recorded in the ionosphere at several longitudes with the European Incoherent Scatter facility. The analysis of these pulsations needs sophisticated signal processing. We found that a detailed description of these pulsations must be made burst by burst. The characteristic parameters are time, frequency, and space extent. Comparison with ground recordings indicates that only the H component is well related to the ionospheric ion velocity. The ionosphere-ground relation is discussed in terms of variability of the auroral conductivity and spatial extent.