A time-lapse recording of a solar storm seen across the Hawke's Bay skyline. Video / Timothy Jones
The solar storm that lit up our night skies over the weekend came just as scientists have been modelling how vulnerable our energy networks are to extreme space weather events - including some far bigger.
Geomagnetic storms occur when explosions of plasma from the sun – called coronal mass ejections – are blasted into space and sometimes collide with Earth’s own magnetic field.
While Earth’s magnetic field shields us from particles from these storms, they’re known to cause problems for power grids by sending extra electrical current down transmission lines – as happened when a Dunedin transformer was knocked out in 2001.
At the weekend, Transpower moved to tackle that risk by taking some lines out of service, and the national grid operator was now reviewing data to gauge the event’s impact.
Also closely monitoring the storm was a team of scientists who’ve been working with the sector on a $15 million project aimed at preparing for a much larger event - a so-called “solar tsunami”.
The effort’s leader, Otago University physicist Professor Craig Rodger, said that if the latest storm was like a magnitude 6.0 earthquake, then his team was exploring the potential impact of an 8.0 shake.
The most powerful solar tsunami in recent times – the 1859 “Carrington Event” - could have caused widespread damage to gas and electricity networks, and railway signals, if it happened today.
Another solar storm in 2012 was of similar magnitude, but it passed Earth’s orbit without striking the planet.
The estimated cost of a major event hitting the United States was between $760m and $4.1 trillion – and for New Zealand, the annualised risk could amount to $1b a year.
“It’s about us making sure that we have the right tools and procedures for it,” Rodger said.
This image provided by Nasa shows a solar flare, as seen in the bright flash in the lower right, captured by Nasa’s Solar Dynamics Observatory on May 9. Photo / Nasa via AP
“This could happen next week, or it could be 100 years from now, but it’s going to happen eventually.”
In one recent study, researchers worked with Firstgas to model potential impacts on gas pipelines, on which voltage had been observed to rapidly change during solar storms.
To protect pipelines from corrosion and disbondment damage – where protective coating separates from the steel pipes within – engineers have designed the systems to cope with changes in the low voltage levels on the pipelines.
Still, Victoria University researcher Dr Tim Divett said, it hadn’t been clear how they’d stand up to a solar tsunami event – so his colleagues collaborated with Firstgas engineers to develop a model to simulate effects.
“The most important result from New Zealand is to know that the largest voltages should be expected at the ends of the pipeline network - that is around Wellington, Taranaki, Northland, Hawke’s Bay, Gisborne and Taupo,” Divett said.
Analysis of how the network responded to the weekend’s large solar storm would be used to further refine the modelling - and give better insight into what could be expected from a Carrington-scale event.
An aurora australis produced a sublime light show in the sky above Hawke's Bay on Saturday night. Photo / Paul Taylor
In another study published last month, a team led by Rodger drew on a decade of data from Transpower to better understand the power grid’s vulnerability to storm-induced fluctuations in voltage and current, called harmonic distortions.
After analysing measurements from nearly 140 sub-stations during 10 geomagnetic storms, the researchers pin-pointed five “hot-spots” that could spread these harmonics wider into the grid.
“We could see that, when geomagnetic disturbances were occurring, they were getting mildly stressed and producing harmonics, which were then flowing into the power grid,” Rodger said.
Their findings not only backed up the results of previous modelling – but were also further somewhat validated during the weekend’s event.
“To see that Henderson in Auckland ‘shone’ in harmonics during storms confirmed that our modelling was likely right.”
Meanwhile, Transpower had drawn its own lessons from the storm for future events – and yesterday was able to re-activate the circuits it took offline without any problems.
“There were some really significant spikes through some of our transformers but not quite at the level you might have expected,” executive general manager of grid development John Clarke told RNZ.
“So, you know, we took good, prudent action. It’s paid off. No consumers lost power.”
Jamie Morton is a specialist in science and environmental reporting. He joined the Herald in 2011 and writes about everything from conservation and climate change to natural hazards and new technology.
