Abstract
Abstract. A physically-based technique for interpolating external magnetic field disturbances across large spatial areas can be achieved with 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, which can subsequently be employed to interpolate or extrapolate the magnetic field across a large area. We show that, in addition to the ionospheric currents, inverting for induced subsurface current systems can result in strong improvements to the estimate of the interpolated magnetic field. We investigate the application of the SECS method at mid- to high geomagnetic latitudes using a series of observatory networks to test the performance of the external field interpolation over large distances. We demonstrate that relatively few observatories are required to produce an estimate that is better than either assuming no external field change or interpolation using latitudinal weighting of data from two other observatories.
Highlights
The geomagnetic field measured on the surface of the Earth is composed of temporally and spatially varying components
There are two classes of technology that are adversely impacted by space weather: those directly affected by variations in the geomagnetic field and those affected by the electric currents induced by the changing field
Pulkkinen et al (2003a) extended the complex image method of Pirjola and Viljanen (1998) to show that the field could be calculated from superposition of the magnetic effect of two horizontal current layers composed of divergence-free elementary current systems
Summary
The geomagnetic field measured on the surface of the Earth is composed of temporally and spatially varying components. Pulkkinen et al (2003a) extended the complex image method of Pirjola and Viljanen (1998) to show that the field could be calculated from superposition of the magnetic effect of two horizontal current layers composed of divergence-free elementary current systems. Their derivation is constructed for a point at radius r between the current system in the ground and in the ionosphere, RG < r < RS for a position (θ,φ) on the Earth. The magnetic field vector (B) at the surface of the Earth is expressed by the superposition of the magnetic
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