A solar "superstorm" could knock out Earth's communications satellites, cause dangerous power surges in the national grid and disrupt crucial navigation aids and aircraft avionics, a major report has found.
It is inevitable that an extreme solar storm - caused by the Sun ejecting billions of tonnes of highly-energetic matter travelling at a million miles an hour - will hit the Earth at some time in the near future, but it is impossible to predict more than about 30 minutes before it actually happens, a team of engineers has warned.
Solar superstorms are estimated to occur every 100 or 200 years, with the last one hitting the Earth in 1859.
Although none has occurred in the space age, we are far more vulnerable now than a century ago because of the ubiquity of modern electronics, they said.
"The general consensus is that a solar superstorm is inevitable, a matter not of 'if' but 'when?'," says a report into extreme space weather by a group of experts at the Royal Academy of Engineering in London.
In the past half century, there have been a number of "near misses" when an explosive "coronal mass ejection" of energetic matter from the Sun has been flung into space, narrowly bypassing the Earth.
In 1989, a relatively minor solar storm knocked out several key electrical transformers in the Canadian national grid, causing major power blackouts.
Similar solar storms significantly increased atmospheric radiation in 1956, 1972, 1989 and 2003, the experts found.
Professor Paul Cannon, who chaired the working group, said the British Government should set up a space weather board to oversee measures aimed at minimising the impact of solar storms.
"A solar superstorm will be a challenge but not cataclysmic. The two challenges for government are the wide spectrum of technologies affected today and the emergence of unexpected vulnerabilities as technology evolves," he said.
"Our message is: 'Don't panic, but do prepare.' A solar superstorm will happen one day and we need to be ready for it.
"Many steps have already been taken to minimise the impact of solar storms on current technology," he said.
Minor solar storms hit the Earth regularly but are far less powerful than the 1859 event named after the British astronomer Richard Carrington, which was the last true solar superstorm.
A similar event today would put severe strain on the electricity grid, where transformers are vulnerable to power surges, as well as degrading the performance of satellites, GPS, aviation and possibly mobile phones.