Review of earth conductivity structure modelling for calculating geo-electric fields

During geomagnetic disturbances the electric field induced by geomagnetic variations drive geomagnetically induced currents (GIC) in conducting networks such as power systems and pipelines. The earth conductivity structure plays an important role in determining the size of the electric field that will be experienced by these systems. The earth conductivity is dependent on rock type and also varies with depth within the Earth. Methods and techniques for modelling different types of earth conductivity structures are reviewed and the advantages and limitations of different models and methods are discussed in this paper. Some methods are advantageous on computation speed while others on the accuracy. Appropriate modelling technique of conductivity structure is important for assessing geomagnetic hazard to power systems.