The use of linear superposition in modelling geomagnetically induced currents

This paper examines how the principle of superposition can be applied to modelling geomagnetically induced currents (GIC) produced by components of the electric field. Localised electric fields can be modelled individually to determine their effect on GIC flows. Also results obtained separately for northward and eastward electric fields can be combined to give the GIC produced by an electric field of arbitrary magnetitude and direction. Formulas are presented for the maximum GIC and the direction of the electric field giving the maximum value. Electric field time series can also be combined with the component model results to give the time series of GIC values. This can be used for geomagnetic hazard assessment by providing an efficient method to determine the GIC produced by historically large magnetic disturbances.