Adaptations to a geomagnetic field interpolation method in Southern Africa

TL;DR

This paper improves geomagnetic field interpolation methods for Southern Africa by adapting the spherical elementary current system approach to include low-cost measurements and mid-latitude conditions, enhancing GIC modeling accuracy.

Contribution

It introduces adaptations to the SECS interpolation scheme for low-cost variometers and mid-latitude regions, addressing regional differences in geomagnetic modeling.

Findings

Inclusion of variometers improves interpolation accuracy.

Mid-latitude adaptations correct previous regional modeling errors.

Useful interpolation results despite initial inaccuracies.

Abstract

Space weather and its impact on infrastructure presents a clear risk in the modern era, as evidenced by the adverse effects of geomagnetically induced currents (GICs) in power networks. To model GICs, ground-based geomagnetic field (B-field) measurements are critical and need to be available in the region of interest. A challenge globally lies in the sparse distribution of magnetometer arrays, which are seldom located near critical power network nodes. Interpolation of the geomagnetic field (B-field) is often needed, with the spherical elementary current system (SECS) approach developed for high-latitude regions favoured. We adapt this interpolation scheme to include low-cost variometers to interpolate dB/dt directly and increase interpolation accuracy. A further adaptation to the scheme is to physically represent the mid-latitude context where most power networks and pipelines lie. The driving current systems in these regions differ from their high-latitude counterparts. Using a physics-consistent mid-latitude version of SECS, we show why previous implementations in Southern Africa are incorrect but still result in useful interpolation. The scope of these adaptations not only has direct application to research in general, but also to utilities, where effective low-cost instrumentation can be used to improve GIC modelling accuracy.