Why are the Northern Lights so often green?
The colors of auroras are determined by the gases in the Earth’s atmosphere, and incoming solar particles tend to collide with different gases at different heights. The most common height for the particles to collide is from 100 to 300 kilometers above the ground. At this height particles hit the oxygen atoms and this creates the familiar green colors. Above the 300 kilometres Lights will turn red and under the 100 kilometer altitude colors will vary. Known colors for Northern Lights are Green, Pink, Red and Green mixture, Pure Red, Yellow, Pure Blue, Orange and White.
Human eye also detects green more readily than other colours. So, it is easier for human to see the Northern Lights in green than other colors. This is also a reason why pictures of Aurora Borealis often show colors that were not visible at the time to the naked eye.
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