Mapping the Northern Lights

An ambitious new project aims to unravel the mysteries of the aurora borealis and the powerful energies involved in our magnetosphere. David Usborne reports

They call it the greatest light show on Earth. Usually confined to the polar latitudes, these swirls of dancing reds and purples briefly fill the night sky and those who witness them can only wonder and gape. For generations, they have fed myths and legends. Are these dazzling pulses of colour in the heavens the celebrations of the gods, or songs of anguish from the spirits of departed men and animals?

They call it the greatest light show on Earth. Usually confined to the polar latitudes, these swirls of dancing reds and purples briefly fill the night sky and those who witness them can only wonder and gape. For generations, they have fed myths and legends. Are these dazzling pulses of colour in the heavens the celebrations of the gods, or songs of anguish from the spirits of departed men and animals?

Now the mystery of the northern lights, also known as the aurora borealis, so-named by the French astrologer Pierre Gassendi in 1621, are set to be unlocked, thanks to a gigantic international research effort now in its final phase of preparation. Called Themis, it is being primarily sponsored by Nasa and the Canadian Space Agency, and involves astronomers and scientists from around the globe.

Collecting the data will be a fleet of five satellites to be launched by Nasa in October 2006. They will be configured to fly in formation over the northern reaches of Canada. The probes will monitor and photograph the northern lights at the moment they occur from a vantage point in space.

Crucially, however, the phenomenon will simultaneously be observed from the ground, thanks to a collection of 20 highly sophisticated digital cameras which are being installed at remote locations all over Canada and Alaska, snapping images of the sky once every five seconds at the very moment that a northern lights eruption occurs.

For scientists like Dr Eric Donovan of Calgary University in Alberta, who is overseeing the placement of the ground-based cameras, the primary goal is simply to understand the energies involved in our magnetosphere that create the displays of light, known as auroral sub-storms or eruptions. Scientists know that solar winds cause the ionisation of gases in space, known as plasmas. But what interests them is what causes the electrical charges suddenly to create new energy - giving rise to the displays.

Dr Donovan likens it to the snapping of an elastic band in space. "It's an important question in science, because this kind of process happens in plasmas all over the universe and probably this is the only plasma we are going to probe directly. We are looking at how energy is stored in one form and then is released violently and changes its form."

But there could be important secondary benefits from the project, including grasping for the first time what triggers the much larger, and more rare, disturbances in the Earth's magnetic field that are called full-blown magnetic storms. Then the borealis can suddenly streak thousands of miles southward, making itself visible even over the United Kingdom and, in North America, as far south as New Mexico.It is on these occasions that the pleasant light show turns into something more menacing.

The biggest storms - they can occur may be 15 times a year - can wreak havoc on our communications systems, affecting everything from the navigation of aircraft, to the proper operation of cash dispensers and the transmission of electricity. One such storm in March 1989 knocked out power across Quebec for nine hours and disabled electricity transformers as far south as New Jersey. "We are on a freight train to gaining knowledge in all these areas," says Dr Donovan, who agrees that understanding the borealis could help scientists predict weather in space and minimise the impact of future storms on communications systems.

Meanwhile, he is rushing to get all his 20 cameras, called All-Sky cameras, in place before the satellites are put aloft, because the cameras and the space probes have to operate in tandem. Working closely with him are researchers at the University of California in Berkeley.

The ground-based cameras will take horizon-to-horizon shots and the key will be to catch the borealis at the very instant that it begins, pinpointing its origins before it spreads all across the sky. The displays can typically last 20-30 minutes. "The scale of this project is staggering," Dr Donovan conceded, noting that three of his cameras were already in place and feeding back data to his headquarters in Calgary. He expects the process of collecting data to continue for about five or six years before any final conclusions will be reached.

Among those assisting in the project is Martin Connors of Athabaska University in Alberta. He is similarly excited about plumbing the mysteries of the aurora borealis with the tens of millions of images that the cameras, also christened "auroracams" will provide. "In addition to seeing it close up, we'll finally be able to take a picture of the whole phenomenon," he said.