Fig. 7From: Estimating ionospheric currents by inversion from ground-based geomagnetic data and calculating geoelectric fields for studies of geomagnetically induced currentsNorth component of the geomagnetic field on 31 May 2013. The spectrum (upper panel: solid) of the geomagnetic field at the surface of the Earth was determined from the Fourier integral of the equatorial electrojet. The time series of the geomagnetic field (lower panel: solid) was obtained by an inverse Fourier transform of the spectrum. The measured data from Fig. 4 (both panels: dotted) is also shown. Location: a Adigrat, b Addis AbabaBack to article page