Present day challenges in understanding the geomagnetic hazard to national power grids

TLDR: In a recent workshop in South Africa, UK and South African scientists and engineers discussed the current understanding of this hazard, as it affects major power systems in Europe and Africa as mentioned in this paper.

About: This article is published in Advances in Space Research.The article was published on 2010-05-03 and is currently open access. It has received 58 citations till now. The article focuses on the topics: Hazard & Natural hazard.

Figures

Figure 3 The complexity of ionospheric current vectors are shown, derived from UK and Scandinavian magnetometer data near the time of the storm commencement during the July 15th 2000 magnetic storm. The scale vector at top left is 8 nT/sec. Coloured spots denote measured GIC at six points in national power grids at the time (red denotes a GIC flowing to the Earth) and in one gas pipeline in Finland. Spot size is proportional to measured current: the largest current in this image was around 11A at the time. Data are courtesy of Finnish Meteorological Institute (IMAGE), Lancaster University (SAMNET), British Geological Survey, Scottish Power plc and Gasum Oy.

Figure 2 The monthly sunspot number (blue line) and monthly CME count during solar cycle 23.The number of CMEs (and consequent geomagnetic activity) tends to follow the sunspot cycle but remains high even as the sunspot number declines. There are only rarely times when the CME count drops to zero or, equivalently, when the likelihood of major magnetic storms disappears. (Sunspot data courtesy of NGDC/NOAA. CME data courtesy of NASA/ESA SOHO/LASCO).

Figure 6 Large storms identified by the peak in the 24-hour running average (aa*) of the 3-hour geomagnetic aa index against time, since 1868, overlain with monthly smoothed solar sunspot number. A threshold of 80 nT has been used to better identify the largest individual storms.

Figure 1 Top: Aurora near LaOtto, Indiana, USA (41.29º geographic north) photographed on 29 October at the time when the CME that emanated from sunspot 486 at 12:18 UT on 28 October 2003 hit Earth's magnetic field, triggered an extreme geomagnetic storm and pushed the auroral oval as far south as Texas. (Photo credit: Robert B. Slobins, as submitted to www.Spaceweather.com). Bottom:

Figure 5 Results of dissolved gas analysis (ppm – left scale) for two similar generator transformers in South Africa (labelled 1 and 2). This illustrates continued gas generation after the short geomagnetic storm (only a few hours) and an apparent sensitivity to transformer loading (MW – same scale) during the following months. The ratios of the different gases also indicate low temperature degradation of paper insulation. Both transformers were removed from service approximately six months after the storm. Note: the dashed lines indicate the increase from nominal pre- to immediate post-storm levels for each data type.

Table 1 The most powerful solar flares recorded since 1976. Those shown in boldface are post year 2000. ‘X-Ray Class’ denotes flare magnitude in units of 10-4 W/m2, between one and eight Angstroms wavelength. Source: http://spaceweather.com/solarflares/topflares.html