New satellites will give 30-minute warning of solar storm emergencies

On Tuesday, the US space agency will launch three space weather satellites that will give an early warning of the worst solar eruptions.

As well as light and heat, the sun also emits intense bursts of radiation in the form of charged particles that spray out across the solar system in what is known as the solar wind.

Earth’s magnetic field usually provides protection from these particles – electrons and charged atoms – by deflecting them into space. It is this interaction that creates the light shows of the aurora borealis and aurora australis – the nothern and southern light.

But serious geomagnetic storms create electrical surges on Earth that have knocked out power grids and brought down satellites, and a Nasa study published last week warned we are likely to experience more as the sun becomes increasingly active.

The sun’s activity fluctuates on an 11-year cycle and can be detected through the number of sunspots on its surface. Since a historical low in 2008, activity has been increasing.

After launch, the three satellites will move into orbit in line with the sun and the Earth, enabling astrophysicists to detect particles on their way towards Earth’s atmosphere. The data will give about 30 minutes’ notice of a coming solar storm, allowing power grids to take emergency action.

“As we’ve become a more technologically dependent society, we’ve become much more sensitive to space weather,” said Tim Horbury, professor of physics at Imperial College London. “More and more of our systems are affected – satellites, communication, navigation. And it’s critical to the survival of astronauts.”

Last year, GPS blackouts caused mayhem for farmers in Canada and the US, who use satellite navigation to plant their crops in perfect rows. Solar storms disrupted GPS twice, which means the smart tractors that planted the crops could not return to exactly the same spot to harvest them.

Those incidents are minor compared with a solar storm that hit Quebec in 1989, causing a nine-hour blackout for 6 million people. “Solar storms drive very large currents into the power grid – they can blow out substations and they take months to build,” Horbury said

The worst solar storm on record caused the Carrington Event of 1859, which triggered electrical surges that made a large proportion of the world’s telegraph lines unusable.

A modern Carrington-level event could cause damage estimated at £2tn – and the risk of an incident is higher than usual.

Horbury and his team at ICL built a crucial sensor on one of the new satellites: two magnetometers sensitive enough to detect the solar wind’s charged particles more than 90 million miles from the sun.

Building a sensitive magnetometer inside the Earth’s much more powerful magnetic field is no easy task. When Horbury’s team tested their equipment at ICL’s South Kensington building at 3am they had to close off the surrounding roads because the tiny electromagnetic field created by car batteries would affect their readings.

The device is able to detect doors opening and closing, Horbury said. It is on an arm that extends away from the Imap satellite (Interstellar Mapping and Acceleration Probe) to protect it from magnetic fields generated by the electronics on board.

These instruments will also help Imap understand how solar wind is formed. Although solar particles are dangerous to life and technology, they also make up the heliosphere, a bubble around the solar system that protects planets from the even harsher radiation arriving from deep space. Some of the sensors will detect the interstellar dust to better understand the galaxy.

Imap will work in tandem with another satellite, SWFO-L1, while the third, the Carruthers Geocorona Observatory, will study the outermost layer of the Earth’s atmosphere where the solar wind arrives.

After the launch, the satellites will take several weeks to reach the Lagrange point, the place where the gravitational force exerted by the sun matches the Earth’s. But more are on their way. ICL and Nasa are already working on HelioSwarm, a constellation of nine satellites to study solar wind turbulence, due to launch in 2028.

Photograph: Nasa/Johns Hopkins APL/Princeton/Ed Whitman