7 times solar storms have affected Earth

Solar storms, which scientists warn could disrupt communications systems this weekend, are recorded as causing chaos on Earth as early as the mid-1800s, when they sparked fires and brought down telegraph systems.

Find out what solar storms are, and how previous events have affected human life.

What are solar storms?

Solar storms are weather events on the Sun that produce a huge release of energy, shooting heat, light and particles of plasma out into space.

In a large eruption, the Sun ejects a flash of heat and light (solar flares), a huge ball of plasma (coronal mass ejections) and sub-atomic particles that can travel at up to 80 per cent of the speed of light (solar energetic particles).

These events can have widespread - and potentially devastating - effects on Earth.

1859: Telegraph machines keep working when unplugged

A solar storm known as the 'Carrington event' disrupted telegraph systems around the world in 1859.

In Boston, telegraph operators reported they were still able to send messages even when they disconnected the machines' batteries, relying instead on the "celestial power induced in the telegraph lines by the magnetic disturbances". The geomagnetic storms sparked fires at other telegraph offices.

A bright glow was visible in the night sky in many parts of the world: Brisbane's Moreton Bay Courier reported that a southern aurora had lit "up the heavens with a gorgeous hue of red".

1882: Telegraph, telephone systems disrupted

A solar storm is blamed for widespread communications problems on November 17, 1882.

The New York Times reported telegraph wires were useless for several hours, resulting in "very much annoyance by reason of the delay in the transmission of business". Telephones were affected too, with people reporting "a buzzing, ringing noise rather than any well-defined sound while attempting communication".

The South Australian Advertiser reported a "magnificent aurora australis" visible in Melbourne, which "at its best resembled a blood-red arch".

1989: Astronauts report burning in their eyes

Astronauts aboard the space shuttle Atlantis were aloft during a solar storm in October 1989, and "reported burning in their eyes, a reaction of their retinas to the solar particles", according to the book Storms From The Sun.

"The crew was ordered to go to the 'storm shelter' in the farthest interior of the shuttle, the most shielded position. But even when hunkered down inside the spacecraft, some astronauts reported seeing flashes of light even with their eyes closed," the book notes, adding that if the astronauts had been on a deep-space mission or working on the Moon, there was a 10 per cent chance they would have died.

1989: Solar storms shut down power grids

In March 1989, space weather events caused transformers to fail, prompting a nine-hour blackout affecting more than 6 million people in Quebec, Canada.

Communications networks around the globe were affected, prompting speculation the Kremlin was jamming radio signals, while short-wave radio frequencies used by commercial pilots also suffered fadeouts.

"In space, some satellites actually tumbled out of control for several hours," NASA says.

Space weather researcher and electrical engineer David Boteler says the 1989 event "is the most significant space weather event for the power industry", and changed many minds about the potential impacts.

"Before 1989, believing in space weather effects on power systems was regarded by some as equivalent to believing in little green men from outer space," he said.

1989: Canadian share trades halted

The Toronto stock market in Canada halted trading after solar activity crashed a series of computer hard drives in August 1989.

Trading was stopped for three hours.

"I don't know what the gods were doing to us," said exchange vice-president John Kane.

2012: Earth has close shave with 'extreme' solar storm

NASA says the Earth had a "perilous" close shave with an "extreme" solar storm in 2012. The storm, believed to be the most powerful solar event in up to 150 years, missed the Earth by about a week.

"If it had hit, we would still be picking up the pieces," Daniel Baker of the University of Colorado said in a NASA statement two years after the event.

NASA scientists said that if Earth had been hit, the event could have knocked our technology back at least 150 years.

2014: Scientists issue solar storm warning

Scientists warn two big explosions on the surface of the Sun will cause a moderate to strong geomagnetic storm on Earth, possibly disrupting radio and satellite communications.

The unusual storm is not likely to wreak havoc with personal electronics but may cause colourful auroras or displays of the Northern Lights across the northern United States.

"We don't expect any unmanageable impacts to national infrastructure from these solar events at this time but we are watching these events closely," said Thomas Berger, director of the Space Weather Prediction Centre at the National Oceanic and Atmospheric Administration.

Are solar storms really that big a threat?

A storm similar to the one that missed Earth by a week in 2012 could have an economic impact of more than $2 trillion, according to a study by the US National Academy of Sciences.

NASA says that is 20 times greater than the costs of Hurricane Katrina, which devastated New Orleans in 2005.

In a February 2014 paper published in Space Weather, physicist Pete Riley of Predictive Science analysed records of solar storms going back more than 50 years and calculated the odds that a storm as big as 1859's huge 'Carrington event' would hit the Earth in the next 10 years; he arrived at a likelihood of 12 per cent.