The freak space weather was caused by a rapid succession of coronal mass ejections, intense eruptions from the surface of the Sun also known as solar flares, which sent a pulse of magnetised plasma hurtling out into space and through the Earth’s orbit. If it had happened just nine days earlier, our world would have been hit, potentially wreaking havoc with the electrical grid, knocking out satellites and GPS and costing economies billions of dollars.
Although very rare, these storms haven’t always passed the Earth by. In 1859, the planet was struck by the so-called Carrington event, which knocked out the telegraph system across the US and literally shocked some of its operators, as the Northern Lights streaked through the sky as far south as Hawaii.
More recently, a small magnetic event in 1989 collapsed Canada’s Hydro-Quebec power grid and led to six million people going without electricity for up to nine hours.
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Luhmann and physicist Ying Liu of China’s State Key Laboratory of Space Weather led a team in analysing the magnetic storm, which was detected by NASA’s STEREO A spacecraft and published their results in Nature Communications.
“An extreme space weather storm – a solar superstorm – is a low-probability, high-consequence event that poses severe threats to critical infrastructures of the modern society,” warned Liu.
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A study last year estimated that a second Carrington event could cost the world $2.6 trillion.
The near-miss storm of 2012 started with a huge outburst on the Sun on July 22, which propelled a magnetic cloud through the solar wind at a peak speed of more than 2,000 kilometres per second, four times as fast as typical magnetic storms. The magnetic eruption tore through the space that Earth had occupied just over a week before, but luckily, Earth and the other planets were on the opposite side of the Sun at the time.
The reason the storm became so fierce is because it was caused by at least two nearly simultaneous coronal mass ejections. Yet another ejection four days earlier had cleared away the materials that would have gotten in the way, allowing the magnetic cloud to work its way up to high speeds.
As well as being a high-speed event, the storm had a southward-oriented magnetic field that lasted for a long time, making it doubly dangerous for Earth. Southern orientation is exactly what the Earth doesn’t want, as it merges violently with the planet’s northward field.
“These gnarly, twisty ropes of magnetic field from coronal mass ejections come blasting from the sun through the ambient solar system, piling up material in front of them, and when this double whammy hits Earth, it skews the Earth’s magnetic field to odd directions, dumping energy all around the planet,” Luhmann said. “Some of us wish Earth had been in the way; what an experiment that would have been.”
“People keep saying that these are rare natural hazards, but they are happening in the Solar System even though we don’t always see them,” she added. “It’s like with earthquakes – it is hard to impress upon people the importance of preparing unless you suffer a magnitude 9 earthquake.”
Scientists haven’t had many opportunities to study solar superstorms, which is exactly why NASA launched STEREOs A and B to record blasts like this one.
“Observations of solar superstorms have been extremely lacking and limited, and our current understanding of solar superstorms is very poor,” Liu said. “Questions fundamental to solar physics and space weather, such as how extreme events form and evolve and how severe it can be at the Earth, are not addressed because of the extreme lack of observations.”