Auroras are the result of charged particles streaming out from the sun getting caught up in Earth's magnetic field and "funneled" back down toward the poles, from where the magnetic field lines originate. When these particles collide with atoms in the atmosphere radiation is emitted across a wide range of the electromagnetic spectrum, including visible light.
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Launched Oct. 17, 2002, ESA's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) is a 4-ton, 16-foot (5-meter) -tall spacecraft designed to observe the universe in high-energy wavelengths, specifically gamma rays from supermassive black holes but also in X-ray and select optical wavelengths. It orbits Earth at distances ranging from 6,200 miles (10,000 km) to 87,000 (140,000 km), outside the most harmful and interfering energy of the radiation belts.
On rare occasions INTEGRAL is aimed toward Earth to block out the background field and allow scientists to calibrate the instruments. It just so happened that this time Earth put on an X-ray performance of its own.
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"Auroras are transient, and cannot be predicted on the timeframe that satellite observations are planned, so it was certainly an unexpected observation," said INTEGRAL Project Scientist Erik Kuulkers. "Although the original background X-ray measurements didn't go quite to plan this time, it was exciting to capture such intense auroral activity by chance."
INTEGRAL is the result of an international collaboration between ESA and the U.S., Russia, the Czech Republic, and Poland, and includes instruments from research teams in Italy, France, Germany, Denmark, and Spain. Learn more about the INTEGRAL mission here.