The most powerful solar storm in more than 20 years has struck Earth’s atmosphere, triggering warnings over the potential disruption to power grids and satellite communications while also producing spectacular celestial light shows in some parts of the world.

The US National Oceanic and Atmospheric Administration (NOAA), which issued a rare solar storm warning, said the solar outburst reached Earth at about 16:00 GMT on Friday, hours sooner than anticipated.

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The first of several coronal mass ejections (CMEs), described as the expulsions of plasma and magnetic fields from the sun, was later upgraded by the NOAA to an “extreme” geomagnetic storm.

It was the first solar storm occurrence since the Halloween storms of October 2003, which caused blackouts in Sweden and damaged power infrastructure in South Africa.

More solar expulsions are expected in the coming days, and possibly into next week, according to the NOAA.

The United States agency alerted operators of power plants and spacecraft in orbit to take precautions.

Fluctuating magnetic fields associated with geomagnetic storms induce currents in long wires, including power lines, which can potentially cause blackouts. Long pipelines can also become electrified, leading to engineering problems.

Spacecraft are at risk from high doses of radiation, although the atmosphere prevents this from reaching Earth.

Following one particularly strong peak, the NOAA’s Space Weather Prediction Center said users of high-frequency radio signals “may experience temporary degradation or complete loss of signal on much of the sunlit side of Earth”.

Unlike solar flares, which travel at the speed of light and reach Earth in about eight minutes, CMEs travel at a steadier pace, with officials putting the current average at 800km (500 miles) per second.

They said that the CMEs emanated from a massive sunspot cluster that is 17 times wider than Earth.

Even pigeons and other species that have internal biological compasses could be affected. Pigeon handlers have noted a reduction in birds coming home during geomagnetic storms, according to US space agency NASA’s Jet Propulsion Laboratory.

The most powerful geomagnetic storm in recorded history, known as the Carrington Event after British astronomer Richard Carrington, occurred in September 1859.

Extreme (G5) geomagnetic conditions have been observed! pic.twitter.com/qLsC8GbWus

— NOAA Space Weather Prediction Center (@NWSSWPC) May 10, 2024

‘Gift from space’

Social media lit up with people posting pictures of auroras from northern Europe and Australasia.

“We’ve just woken the kids to go watch the northern lights in the back garden! Clearly visible with the naked eye,” Iain Mansfield in Hertford, England, told the AFP news agency.

That sense of wonder was shared in Australia’s island state of Tasmania.

“Absolutely biblical skies in Tasmania at 4am this morning,” photographer Sean O’Riordan posted on X alongside a photo.

The storm could also produce northern lights as far south in the United States as Alabama and across northern California, according to the NOAA.

But it was hard to predict and experts stressed it would not be the dramatic curtains of colour normally associated with the Northern Lights, but more like splashes of greenish hues.

“That’s really the gift from space weather – the aurora,” Rob Steenburgh, a scientist with the Space Weather Prediction Center, told The Associated Press news agency.

The Northern Lights seen over the National Monument of Scotland in Edinburgh during the most powerful solar storm in more than 20 years [Jacob Anderson/AFP]