Changes in the space environment caused by the Sun can lead to periods of bad "space weather." As well as driving intense displays of the northern lights (or aurora borealis), this can generate unexpected currents in electricity distribution grids that could lead to blackouts and damage to valuable infrastructure with potentially high cost to the global economy.
Now a team of British scientists at Lancaster University and the British Geological Survey (BGS) in Edinburgh have developed a new model that shows the widespread impact inclement space weather could have on the UK. On April 14th, team member Katie Turnbull presented the results at the RAS National Astronomy Meeting (NAM 2010) in Glasgow.
Bad space weather can cause fluctuations in the Earth's magnetic field (geomagnetic storms) that lead to Geomagnetically Induced Currents (GICs) in power grids. These currents have previously been blamed for blackouts in Canada and Sweden and are suspected of damaging power transformers in countries at lower latitudes. Large GICs have even been recorded in Scotland.
To prevent future blackouts, understanding how GICs occur is vital. The model developed by the British team, the most sophisticated yet developed, takes magnetic field measurements from all over the UK and combines them with the BGS's 3D model of how the ground beneath the UK conducts electricity, in order to estimate the currents induced at over 250 locations in the high voltage national grid.
The new work provides further evidence that the size of the unwanted current depends not only on the severity of the geomagnetic storm but also on the configuration of the power grid and the direction and fluctuation speed of the electric fields produced. For many years, it was thought that only countries located at high latitudes (near to the Earth's magnetic poles) were at risk, but this is now known not to be the case. While the basic physics that links solar activity to our electricity grids is broadly understood, the interaction between natural and man-made systems makes it hard to quantity the risks.
Results to be presented at the conference will compare simulated GICs in the UK grid model with those actually measured during a geomagnetic storm in February 2003. The simulated and measured currents are similar, but the model suggests that high currents are likely to be induced at several locations in the grid where GICs were not being monitored by the power industry at the time.
Although in this case no damage was caused, the scientists plan to use the model to learn how the UK grid might respond to possible future space weather events. Damaged transformers are not cheaply or easily replaced and some scientists and engineers are concerned that a major disturbance, like the severe magnetic storm that followed the solar flare observed by English astronomer Richard Carrington on the morning of 1st September 1859, could interrupt the worldwide electricity supply network by simultaneously disabling hundreds of transformers.
Known as the Carrington flare, this was the first flare ever observed and the storms around that time were the first recognised space weather events. In a related presentation on April 15, Ellen Clarke and colleagues at BGS and co-workers at the British Antarctic Survey and the University of Otago in New Zealand have estimated the strength of the solar flare witnessed by Carrington.
They correlated recent flares of known X-ray strength against the related magnetic variation, or 'solar flare effect', which is seen in geomagnetic records. The team then used this relationship with the measured Carrington 'solar flare effect', recovered from the 150 year old geomagnetic recordings made at Greenwich and Kew observatories and now held in the BGS archives in Edinburgh. They estimate that the Carrington flare must have been about twice as large (in X-ray flux) as the flare that preceded the largest geomagnetic storm of the last 10 years and that affected the Swedish power grid.
150 years ago the effect of GICs was limited to causing chaos in the telegraph network, but a storm like this would today have a wider impact. The US National Academies estimate the cost of such a future severe geomagnetic storm scenario hitting the USA to be 1-2 trillion dollars in the first year. Depending on the damage, they believe that full recovery could then take 4-10 years.
Lancaster University scientist and team member Dr Jim Wild stresses the wider importance of the group's new research. "The science is still in a relatively early stage and we're only just starting to understand the interplay between complex natural and manmade systems."
BGS Geomagnetism team leader Dr Alan Thomson added "a major objective is to shed light on the impact of both everyday and extreme space weather on our technologies and therefore to be better aware of the risk."
"Research in this area spans space science and geophysics -- we hope that this kind of multi-disciplinary science will be a priority for the UK's newly-launched Space Agency" added Dr Wild.
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