An example of how transfer functions represent the geomagnetically electric currents (GIC) flowing through a particular transformer, in this case at Dunedin on New Zealand’s South Island. The seven colored curves shows the modelled GIC as a function of the magnetic field variation (dB/dt), with the colors indicating the response to different periods of variation from two or over five hundred minutes, and the polar angle indicating the response to changing orientations of dB/dt. This highlights that the greatest GIC in this transformer arises in response to south-west or north-east orientations of dB/dt. Credit: Ingham et al., 2017, Figure 7a
Source: Space Weather

A key topic in space weather research is how to model the geomagnetically electric currents (GICs) that can flow through electrically grounded infrastructures, particularly power grids. Ingham et al. [2017] use a transfer function approach which numerically models how GICs respond to changes in the local geomagnetic field. They applied this to an extensive GIC dataset for the New Zealand power grid (available thanks to the authors’ good working relationship with the grid operator) and developed insights into the levels of GIC present in the New Zealand grid when serious disruption and damage to grid assets occurred during a November 2001 geomagnetic storm. With suitable scaling, this modelling is also used to produce simulated GIC time series for a Carrington-class geomagnetic storm. Such time series are a valuable aid to assessing, and planning for, future extreme space weather events. They can provide food for thought by all concerned with space weather risks.

Citation: Ingham, M., Rodger, C. J., Divett, T., Dalzell, M., & Petersen, T. [2017]. Assessment of GIC based on transfer function analysis. Space Weather, 15.

—Michael Hapgood, Editor, Space Weather

Text © 2018. The authors. CC BY-NC-ND 3.0
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