There are many interactions between the Sun and the Earth but one of the most dynamic events is a ‘substorm’ - an explosive reshaping of the Earth’s outer magnetic field.

To better understand substorms, scientists in Europe and North America are studying them from space using the Time History of Events and Macroscale Interactions during Substorms (THEMIS) satellites launched by NASA in 2007 and from the ground using a network of all-sky cameras.

University of Lancaster solar-terrestrial scientist Dr Emma Woodfield gave a talk at the Royal Astronomical Society National Astronomy Meeting in Belfast and presented the first few months of results from the Rainbow cameras newly installed in southern Iceland that complement this network.


Rainbow camera image taken from just after substorm onset on 1 February 2008, Credit: Dr. James Wild, Lancaster University.

Best seen from within the Arctic and Antarctic Circles, the northern and southern lights (aurora borealis and aurora australis) are the most visible way in which the Sun affects the upper atmosphere and magnetic field of the Earth. More severe consequences of the interaction between the Sun and the Earth include disruption to radio communications, GPS systems and satellite electronics and overloaded power grids.

This has made understanding ‘space weather’ a priority for physicists around the world.

Substorms result from a build up of energy deposited by the solar wind into the near-Earth environment and at their onset there is a dramatic increase in the intensity and activity of the aurora. The ground-based Rainbow cameras designed by the University of Calgary, Canada, track rapid changes in the aurora by taking full colour images of the whole sky through a fish-eye lens every 6 seconds.

To fully understand the nature of substorms and to distinguish between the main competing models describing the substorm process there has been a dramatic increase in the number of these ground instruments across Canada and the northern United States. This makes it possible to “join up the dots”, linking what goes on further out in space seen by the THEMIS satellites with the phenomena observed closer to home.

Scientists from Lancaster University have now put into place the first of three cameras that will bridge a gap in coverage between North America and mainland Europe. The ‘Rainbow’ camera was installed at a site maintained by the University of Leicester near Þykkvibær in southern Iceland in October 2007.


The Rainbow camera images captures a quiet auroral arc erupting rapidly at substorm onset, 1 February 2008. © and credit: Dr. James Wild, Lancaster University.

In her talk, Dr Woodfield's images and movies from the Rainbow camera showing the dramatic changes in aurora structure following the onset of a substorm. She is upbeat about the results to date.

“We have had a wonderful first observing season. Now the hard work really begins as we sift through the data for vital clues to how a substorm really works.”