POLAR spacecraft answered this by photographing an auroral oval surrounding the north pole of the Earth, causing displays on both the night and day side. The auroral sub-storm, pictured in false-color above, developed within 15 minutes and may have lasted as long as on hour. Aurora are caused by charged particles streaming away from the Sun and towards the Earth. As the particles fall to Earth, they spiral along magnetic field lines and cause colorful radiation. The UVI experiment onboard the POLAR spacecraft is equipped with special filters that allow it to see aurora in a band of ultraviolet light where sunlight is relatively dim. The more red the emission depicted in the above photo, the more intense the radiation. Earth's continents have been drawn in for clarity
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Based on Astronomy Picture Of the Day
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