NASA - National Aeronautics and Space Administration

Time History of Events and Macroscale Interactions during Substorms (THEMIS) is a two-year mission consisting of five identical probes and a network of ground observatories that will track and determine the cause of the violent eruptions of auroras that occur during substorms. When the five identical probes align over the observatories on the North American continent, scientists will collect coordinated measurements along the sun-Earth line, allowing the first comprehensive look at the onset of substorms and how they trigger auroral eruptions. Credit: NASA

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