OR/14/004 Discussion and conclusions

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Thomson, A W P (Editor), Beggan, C, Kelly, G, Baillie, O, Viljanen, A, and Ngwira, C. 2014. Project EURISGIC: worst case scenarios (Technical note D5.1). British Geological Survey Open Report, OR/14/004.

It is probably fair to say that at the present time (2013–2014) research into worst case geomagnetic storm scenarios, and extreme geomagnetic events, is still evolving. Partly driven by scientific curiosity and partly by demands from stakeholders, such as governments and industry bodies, there is much activity, but also some degree of convergence, for example, on extreme levels of geoelectric fields and dB/dt. However caution is required as there may yet be some new physics or new event data that could still be found. Indeed, digitisation of historical analogue magnetograms (e.g. in WP8 of EURISGIC) is now bearing fruit and may yet change our perception of the meaning of ‘extreme’. The geoelectric field results also suggest caution in simple extrapolations, given that some asymptotic maximum level may be present in (some) mid-latitude and sub-auroral data.

However even from the present understanding of extreme geophysical data we can already infer likely extremes in GIC and a number of papers have shown levels in the region of hundreds of Amps per substation, for the UK, Europe and other systems. This is important information for grid operators, in terms of how these Amps are distributed amongst individual transformers of differing type and age. The results also help address whether current levels of ‘GIC-proofing’ specified for new transformers are likely to be adequate.

It is likely that in the short to medium term that research will continue along the lines indicted in the introduction: through EVS, theoretical and event studies, which in combination will hopefully reveal the true nature of geomagnetic extremes. There are also other data sets for which extreme event analysis is already planned. EVS techniques have not yet been applied to the long record of solar wind data, particularly the southward component of the interplanetary magnetic field. Also, analysis of the complete Nagycenk electric field data is planned, but will take time to process.