Interpolation of magnetic and electric fields using spherical elementary current systems

A physics-based technique for interpolating magnetic and electric field disturbances of external origin across large spatial areas can be achieved by employing the Spherical Elementary Current System (SECS) method using data from ground-based magnetic observatories. The SECS method represents complex electrical current systems as a simple set of equivalent currents placed at a specific height in the ionosphere. The magnetic field recorded at observatories can be used to invert for the electrical currents and subsequently employed to interpolate or extrapolate the electric and magnetic field across a large area at midto high geomagnetic latitudes. Here we show that the magnetic field interpolation can be improved, even over very large distances (>; 1000 km), by the addition of further observatory data into the SECS inversion.