William Atkins
Friday, 25 July 2008 02:44
Science -
Space
Page 2 of 3
THEMIS scientists observed the beginning of magnetic substorms using the five THEMIS satellites, along with a network of twenty ground observatories located throughout Canada and Alaska. Sixteen observatories—located in such places as Inuvik, Whitehorse, Prince George, Goose Bay and at the Ekati Diamond Mine—were installed across Canada by University of Calgary scientists, while another four observatories were installed in Alaska by SSL.
The five
THEMIS satellites observe together once every four days as they line up above the Earth’s equator. As they make their coordinated observations, the ground observatories are also making sightings in parallel with their space partners.
Each ground station consists of a magnetometer and a camera that are used to determine where an auroral substorm will begin. Instruments measure the auroral light from particles flowing along Earth's magnetic field and the electrical currents these particles generate.
During each alignment, the satellites capture data that allow scientists to precisely pinpoint where, when, and how substorms measured on the ground develop in space.
Then, on one important day--February 26, 2008--during one such THEMIS lineup, the satellites observed an isolated substorm begin in space, while the ground-based observatories recorded the intense auroral brightening and space currents over North America.
These observations confirmed for the first time that magnetic reconnection triggers the start of these magnetic substorms.
The discovery supports the theory behind magnetic reconnection of substorms. The theory asserts that all substorms follow a particular pattern when first forming. This pattern consists of a period of reconnection, followed by rapid auroral brightening and rapid expansion of the aurora toward the poles. This culminates in a redistribution of the electrical currents flowing in space around Earth.
This discovery is important to us on Earth. Please read on for an explanation.
