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A magnificent type-A aurora reaches high into the sky over Fairbanks, Alaska.   This sheet of color extends vertically through the atmosphere, and its rays trace out the Earth's magnetic field lines.  The red light is created by glowing oxygen more than 120 miles above the Earth's surface, while the green originates much lower―only about 60 miles up.  This green light, however, is so intense that it sometimes even tints the snow green!