Abstract. An analysis of the man made contamination on ULF measurements in highly populated areas has been conducted at several suitably chosen sites in Western Europe. The experimental results show common characteristics at different stations with clear evidence for an additional working day contamination with respect to weekends. These effects more clearly emerge in the vertical component that is less influenced by natural signals. A similar analysis conducted at Terra Nova Bay does not reveal any clear evidence for man made disturbances on Antarctic measurements.

Key words. (Magnetospheric physics, instruments and techniques; Solar wind-magnetosphere interaction) (Geomagnetism and paleomagnetism time variations, diurnal to secular)