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This research focuses on the inversion of geomagnetic variation field\udmeasurement to obtain source currents in the ionosphere. During a geomagnetic\uddisturbance, the ionospheric currents create magnetic field variations that\udinduce geoelectric fields, which drive geomagnetically induced currents (GIC)\udin power systems. These GIC may disturb the operation of power systems and\udcause damage to grounded power transformers. The geoelectric fields at any\udlocation of interest can be determined from the source currents in the\udionosphere through a solution of the forward problem. Line currents running\udeast–west along given surface position are postulated to exist at a certain\udheight above the Earth's surface. This physical arrangement results in the\udfields on the ground having the magnetic north and down components, and the\udelectric east component. Ionospheric currents are modelled by inverting\udFourier integrals (over the wavenumber) of elementary geomagnetic fields\udusing the Levenberg–Marquardt technique. The output parameters of the\udinversion model are the current strength, height and surface position of the\udionospheric current system. A ground conductivity structure with five layers\udfrom Quebec, Canada, based on the Layered-Earth model is used to obtain the\udcomplex skin depth at a given angular frequency. This paper  presents\udpreliminary and inversion results based on these structures and simulated\udgeomagnetic fields. The results show some interesting features in the\udfrequency domain. Model parameters obtained through inversion are within\ud2% of simulated values. This technique has applications for modelling\udthe currents of electrojets at the equator and auroral regions, as well as\udcurrents in the magnetosphere

Applying inversion techniques to derive source currents and geoelectric fields for geomagnetically induced current calculations