Solar storm hitting Earth causes spectacular aurora displays

A large solar storm has caused spectacular aurora displays across the Northern Hemisphere after blasting out of the Sun three days ago.

On 1 August, almost the entire side of the Sun that faces the Earth erupted in a blaze of activity known as a "coronal mass ejection". These storms throw up to 10 billion tons of plasma - superheated gas - off the surface of the star and hurtling into space at around a million miles an hour. It covered the 93 million mile journey from the Sun to the Earth in just three and a half days.

It was the "first major Earth-directed eruption in quite some time," according to Leon Golub, a scientist at the Harvard-Smithsonian Center for Astrophysics (CfA), who warned of the event on Monday.

The flare which caused the eruption was relatively small, described as a class C3 by astronomers. Other flares, known as X or M class, are much larger, and capable of doing damage on Earth. C-class flares rarely have much effect on Earth beyond auroras - the glowing displays towards the poles, like the Northern (and Southern) Lights.

Dramatic auroras were seen in Denmark, Norway, Greenland, Germany and across the northern United States and Canada as the expanding bubble of gas slammed into the Earth's atmosphere. The frequently beautiful displays are caused by the charged particles in the plasma interacting with the Earth's magnetic field - the solar matter is drawn towards the poles, where they collide with nitrogen and oxygen atoms in the atmosphere.

While no damage seems to have been done by this flare, Nasa astronomers have previously warned that a much larger solar storm could cause havoc with electrical systems on Earth. In 2013, the Sun is expected to reach a stage in its roughly 11-year cycle when large storms are more likely.

In 1859, one huge flare burned out telegraph wires across Europe and the USA. The so-called "Carrington flare", named after its discoverer, “smothered two-thirds of the Earth’s skies in a blood-red aurora a night later, and crippled all global navigation and global communication, such as it was at that time. Compasses spun uselessly and the telegraph network went down as phantom electricity surged through the wire,” according to Dr Stuart Clark, author of The Sun Kings.

More recently, in 1989, a smaller but still enormous storm caused the power grids in Quebec to go down for nine hours, causing hundreds of millions' worth of dollars in lost revenue.