The eerie glow of the ?Northern Lights? (credit: Darren Wright, University of Leicester)

The eerie glow of the ?Northern Lights? (credit: Darren Wright, University of Leicester)

The northern lights

On a clear night over the far northern areas of the world, you may witness a hauntingly beautiful light display in the sky. The eerie glow of the ?Northern Lights? is exquisite. The display, often resembling a slow-moving ribbon silently undulating in the sky, is called the Aurora Borealis. It is also visible in far southern regions around the South Pole (the Aurora Australis).

Occasionally, however, the aurora becomes much more dynamic. The single auroral ribbon may split into several ribbons or even break into clusters that race north and south. This dynamic light show in the polar skies is associated with what scientists call a magnetospheric substorm.

On 19th February this year, five satellites were loaded into a single rocket and launched from NASA’s Cape Canaveral complex in Florida. Their two-year mission is called THEMIS, in honour of the blindfolded Greek goddess of order and justice. More technically, THEMIS stands for Time History of Events and Macroscale Interactions during Substorms. The project aims to discover when, where and why solar wind energy stored in the magnetic field in the Earth's upper atmosphere is released, propelling showers of electrons into the atmosphere and creating some of the most dynamic auroral displays to be seen: the famous Northern Lights, or their opposite polar counterpart, the Southern Lights (Aurora Borealis and Aurora Australis).

Previous single-satellite investigations have been unable to pinpoint the exact origin of these aurorae. The five THEMIS satellites align in their orbits once every four days, allowing comprehensive measurements that will trace the triggering mechanisms of magnetospheric substorms. Simultaneously, a massive network of ground-based cameras specifically designed to image the entire sky in a single exposure will record the explosive auroral displays associated with substorms. Scientists at Lancaster University are deploying auroral cameras on Iceland to contribute to this mission, bridging the gap between cameras in North America and Scandinavia.

Funded by STFC suntrek