Green Comet

Cloud of the Day – Aurora

Aurora is not clouds. Clouds can’t form in the tenuous wisps of atmosphere found at the heights, approximately 90 – 1,000 kilometers, where aurora occurs. Therefore, it is wrong for me to call aurora the cloud of the day. Naughty me. It’s a meteorological phenomenon, and it’s beautiful. I’ll call it the cloud of the day if I want.

The Northern Lights, aurora borealis, were named in 1621 by Pierre Gassendi, a French scientist, priest and philosopher. Boreas was the Greek name for the north wind, and Aurora was the Roman goddess of the dawn. The Northern Lights are mirrored around the south pole by aurora australis, the Southern Lights.

The aurorae work on the same principle as a neon lamp. Energized atoms release the excess energy as photons of light. In a neon lamp, the atoms are energized by electricity. In aurorae, nitrogen and oxygen atoms are energized by the solar particles that are trapped and funneled into the upper atmosphere by Earth’s magnetic field. When intense enough to be more than a whitish glow, the most common colors are green from oxygen and red from nitrogen. Other colors result from mixing of the main colors, or from variations in the excitation-release mechanism. For example, the rare blue that sometimes comes from nitrogen.

Although it might be interesting, there is no precipitation from aurora.

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