Polar lights give up some secrets

[Rick]

The sudden flare-ups and rapid movement sometimes seen in the Northern and Southern Lights can now be explained in fine detail, say scientists.

They say the phenomenon is driven by huge releases of stored energy that occur more than 100,000km away in the Earth's protective magnetic shield.

The explosive events arise when stressed magnetic field lines suddenly snap to a new shape.

The information comes from five Nasa satellites flying around the Earth.

More: http://news.bbc.co.uk/2/hi/technology/7524069.stm