THEMIS (Time History of Events and Macroscale during Substorms)

The northern lights are powered by a stream of charged particles that flow out from the sun. Blown towards the earth at 400 kilometers a second, this solar wind causes storms in the magnetic field near the North and South Poles.

But what factors trigger the storms? What causes these charged particles to suddenly explode into dancing columns of light that flit across the sky?

The Canadian Space Agency and the National Aeronautical Space Administration (NASA) are working together on THEMIS to answer these questions. As a network of 20 ground-based observatories (GBO) captures and analyses data from the northern lights, five small NASA satellites, flying in constellation, measure changes in space. Scientists can then compare the satellite data with the observations made on the ground as they refine current theories. More information can be found at

With this mission, scientists from the U.S., Canada, and Europe, under the lead of researchers from the University of California at Berkeley, will advance our understanding of processes occurring around the sun and other stars.

The Canadian THEMIS science team is responsible for the 16 ground observatories in northern Canada. Led by the University of Calgary, other partners include Athabasca University, the Universities of Alberta, New Brunswick, and Saskatchewan, and Natural Resources Canada.

Each THEMIS site has a local custodian who has easy access to the GBO, particularly during the winter months when the long nights make conditions ideal for auroral observation. The custodian is responsible for the routine maintenance and upkeep of the observatory, including periodic removal of snow from the dome and satellite dish, removal and shipment of the data disk to the University of Calgary, and occasionally some minor trouble shooting.  The Aurora Research Institute (ARI) provides these services for the THEMIS site in Inuvik - the most northern THEMIS site in Canada.

The above description was adapted from for use on the ARI website, with the permission of the University of Calgary.