Those who live in mid to high latitudes can often see the aurora, the so-called Northern or Southern Lights.

It can take many forms, curtains, arcs, bands and rays of shimmering red or blue light.

It is caused by the impact of charged particles from the sun striking the earth's upper atmosphere. As they head towards the earth these particles are channeled towards the planet's magnetic poles.

To see what's happening a camera sensitive to ultraviolet light has been placed on a polar orbiting spacecraft.

As seen from space - the arc over the pole

It was during a geomagnetic storm in 1997 that scientists observed that the aurora was behaving oddly.

They described their observations at a meeting of the American Geophysical Union.

"We observed polar arcs form from both the dusk and dawn sides of the pole at the same time" said Dr James Spann, of NASA.

Such polar arcs are rare. The first to be seen was detected in 1985. Scientists are at a loss to explain them.

Monitoring aurora from space is important. They occur along with a so-called geomagnetic storm when the earths magnetic field can fluctuate. This can induce power surges in satellites and power lines and cause communications interference.