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Aurora From Space
"Auroras are caused by electrons and protons from space raining down on Earth's atmosphere. The solar wind, through a set of complex and fascinating interactions with the Earth's magnetic field, is the ultimate source of energy that drives these particles toward our planet. When they hit the top of the atmosphere, they excite atoms and molecules and make the air glow. Reds and greens come from atomic oxygen, blues from nitrogen.
These colorful lights range in altitude from 80 km to 500 km above Earth's surface."
from
Space Station Astrophotography (NASA)
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