The researchers used five Nasa satellites to monitor the northern lights
The secrets of the Northern Lights, one of the world’s greatest natural spectacles, have been unlocked by scientists.
The ghostly displays that illuminate the skies above the Arctic have inspired myths and captivated onlookers for centuries, but now researchers have discovered more about how they are created.
The lights, also known as Aurora Borealis, are generated when electrical tornadoes hurtle towards Earth and come into contact with the ionosphere, one of the upper layers of the atmosphere.
These tornadoes, spinning at more than a million miles an hour, are produced by vast clouds of solar particles.
They gather 40,000 miles above the planet’s surface, releasing whirlwinds when they become destabilised by the strength of their own electrical charge.
Astronomers have long known that the lights are created when streams of particles from the sun – known as solar winds – come into contact with the Earth’s magnetic field.
But a team including Professor Karl-Heinz Glassmeier of the Institute for Geophysics and Extraterrestrial Physics in Braunschweig, Germany, has now established how the field traps the particles on the planet’s sun-facing “day” side, before deflecting them to the “night” side, where they gather in clouds and then dive towards the surface.
The researchers used five Nasa satellites sent up as part of the Themis programme to monitor the Northern Lights – and their equivalents at the south pole – to produce the first images of these tornadoes, and discussed their findings at a European Geosciences Union meeting in Vienna last week.
“The Themis satellites have given us our first opportunity to see the process that generates the aurorae in three dimensions and show just what spectacularly powerful events they are,” Prof Glassmeier said.