8-12 July 2013
Inversion of Geomagnetic Fields to Derive Ionospheric Currents that Drive Geomagnetically Induced Currents.
Presented by Dr. Jean DE VILLIERS on 10 Jul 2013 from 17:40 to 18:40
Type: Poster Presentation
Track: Track D2 - Space Science
This research focusses on the inversion of geomagnetic field measurement to obtain source currents in the ionosphere. The ionospheric currents during a geomagnetic storm induce geo-electric fields, which in turn create geomagnetically induced currents (GICs) in power lines. These GICs may cause damage to grounded power transformers. The ultimate aim is to develop a system for predicting the ionospheric source currents from solar event data and use the link between the source currents and GICs to provide advance warning to power utilities. Line currents running East-West along given latitude are postulated to exist at a certain height above the Earth’s surface. This physical arrangement expresses the fields on the ground in terms of the magnetic north and down component, and the electric east component. Ionospheric currents are modelled by inverting Fourier integrals of elementary geomagnetic fields using the Levenberg-Marquardt technique. The output parameters of the model are the current strength, period, height and latitude of the ionospheric current system. A conductivity structure with five layers from Quebec, Canada, based on the Layered-Earth model, is used to obtain the complex skin depth at a given angular frequency. The paper will present inversion results based on the Quebec structure and simulated geomagnetic fields. Model parameters can be obtained to within 2% of published values. This technique has applications for modelling the currents of electrojets at the equator and auroral regions, as well as currents in the magnetosphere.