Geomagnetically Induced Currents (GIC) in power networks as a source of electromagnetic sounding data

Geomagnetically Induced Currents (GIC), which can flow in technological systems such as power transmission grids, are a consequence of the geoelectric field induced at the surface of the Earth during geomagnetic storms. Since 1999 the British Geological Survey have, in conjunction with Scottish Power Plc, been monitoring GIC at four sites in the Scottish Power high-voltage transmission network. The main purpose of the monitoring project is to try to understand the risk posed to the power network by GIC. However, this poster investigates the feasibility of using GIC data in order to investigate long-period induction in the central Scotland and northern England region. We have already investigated the joint spectral characteristics of the GIC and geomagnetic observatory data from Eskdalemuir in the Scottish Borders, and GIC have been shown to be coherent with magnetic field variations in a period range which extends from 10-2,000s. In addition, we found that the phase response of a frequency dependent bi-variate transfer function model of the physical link between magnetic field variations and GIC may be interpreted in a similar manner to Magnetotelluric impedance phases. However, the quality and long period resolution are limited by the available data which is mostly collected in 12-24 hour segments. Therefore, the possibility of extending the period range, and optimising the quality of the data, by collecting and analysing longer segments of data, is investigated