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The Winter 2010 issue of The Earth Scientist includes a variety of educational resources, ranging from astronomy to glaciers. Check out the other publications and classroom materials in our online store.
This aurora display includes green light emissions from oxygen atoms as well as a purple glow produced by nitrogen molecules.
Click on image for full size
Image courtesy of Jan Curtis.

Colors of the Aurora

The aurora (Northern Lights and Southern Lights) are caused by collisions between energetic particles in Earth's magnetosphere and atoms or molecules in the upper atmosphere. Particles, mostly electrons and protons, are accelerated to high speeds and energies as they spiral along Earth's magnetic field lines. The particles bounce back and forth between Earth's magnetic poles, where magnetic field lines dip into the planet's upper atmosphere. Some of the energetic particles collide with atoms and molecules of oxygen and nitrogen in the upper atmosphere near the poles.

These collisions add energy to the atoms, which in turn shed the excess energy by emitting light. The brilliant displays of auroral lights have characteristic colors which depend on the type of atoms or molecules which are giving off the light. Oxygen atoms emit green light that is seen in many auroral displays. Oxygen atoms above 150 km (93 miles) in altitude can also give off red light. Energized nitrogen molecules emit red, blue, and violet light.

Last modified March 29, 2010 by Randy Russell.

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