Catching a glimpse of auroras – as many of us had the chance to do back in May when the most severe geomagnetic storm in two decades hit – is on most of our bucket lists.
Yet stunning though they may be, scientists are becoming increasingly nervous about the potential threats they pose to modern infrastructure.
Now, new research has highlighted the connection between these natural light shows and strong electric currents triggered by magnetic forces – also known as geomagnetically induced currents, or GICs – that can damage vital infrastructure, such as pipelines and submarine cables.
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Scientists have found that the angle at which interplanetary shocks strike Earth's magnetic field is crucial in determining the strength of these currents.
"Auroras and GICs are driven by the same space weather events," said Dr Denny Oliveira from NASA's Goddard Space Flight Center, the lead author of the study published in Frontiers in Astronomy and Space Sciences. "The aurora is a visual warning that indicates that electric currents in space can generate these GICs on the ground."
When particles ejected from the Sun interact with Earth's magnetic field, they create geomagnetic storms that interact with Earth's atmosphere, forming auroras. Interplanetary shocks, a kind of shockwave emanating from the Sun’s solar wind, also contribute to this phenomenon.
As Oliveira explained, interplanetary shocks form in a similar way to a sonic boom from a jet that breaks the sound barrier. When the speed of solar wind approaching Earth exceeds its own 'sonic speed barrier', a shockwave forms. Only here, instead of forming a boom of sound as with a jet, it forms as a magnetic shockwave which can compress Earth's magnetic field.
It's such a shockwave that can generate strong currents that pose a risk to any infrastructure conducting electricity. Stronger interplanetary shocks result in more powerful currents and auroras – but frequent, less intense shocks can also cause significant damage over time.
Oliveira added, “Arguably, the most intense harmful effects on power infrastructure occurred in March 1989 following a severe geomagnetic storm – the Hydro-Quebec system in Canada was shut down for nearly nine hours, leaving millions of people with no electricity.
“But weaker, more frequent events such as interplanetary shocks can pose threats to ground conductors over time. Our work shows that considerable geoelectric currents occur quite frequently aftershocks, and they deserve attention.”
The research team discovered that shocks hitting Earth head-on produce higher peaks in geomagnetically induced currents both immediately after impact and during subsequent storms.
The predictability of angles of the interplanetary shocks, up to two hours before impact, means experts could use these findings to implement protective measures for vulnerable infrastructure before the strongest shocks hit.
“One thing power infrastructure operators could do to safeguard their equipment is to manage a few specific electric circuits when a shock alert is issued,” suggested Oliveira.
“This would prevent geomagnetically induced currents reducing the lifetime of the equipment.”
We’re not out of the woods yet, though. Oliveira explains that further research is necessary to protect critical infrastructure effectively from the biggest shockwaves facing Earth.
About our expert
Denny Oliveira is a space physics researcher in the Geospace Physics Laboratory of NASA Goddard, affiliated with PHaSER /UMBC. His research is centred on interplanetary shocks, including those generated by coronal mass ejections, and their influence on plasma processes in the geospace.
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