Interpolation of electric and magnetic fields using Spherical Elementary Current Systems

Estimation of the external (to the Earth’s surface) electric or magnetic field disturbances at a point remote from an observatory can be difficult. We show how interpolation of electric field disturbances in the ionosphere can be achieved with the Spherical Elementary Current System (SECS) method using data from a number of ground-based magnetic observatories. The SECS method represents the complex electrical currents in the ionosphere as a simple set of equivalent currents placed at a specific altitude. The resultant magnetic field recorded at observatories can be used to invert for the electrical currents use this to interpolate the magnetic field. Here we apply the SECS method to auroral zone latitudes using a series of observatories to test how well the external field can be interpolated over large distances. We demonstrate that relatively few observatories are required to produce an estimate which is better than the null hypothesis (i.e. assuming no change).