What Causes the Auroral Lights?

Protons and electrons from the Sun travel along the Earth's magnetic field lines and impact the atmosphere. Atmospheric gases are electronically excited by these collisions and give off different types of light. The color and altitude of the auroral lights tell us which atmospheric gases are being excited.

Below 60 miles in altitude, nitrogen is responsible for blue and red auroral light.
Above this to 150 miles, green light is produced by oxygen atoms.
Above 150 miles, red light from oxygen dominates the auroral lights.

Since blue, green and red light are produced in various combinations it mixes to give a variety of colors (such as purple and pink).

This animation demonstrates very simply how different elements at different heights, let off energy that we see as different colors. You'll notice in the static aurora picture, it almost seems as if there are layers of colors one on top of the other.
Movie adapted from original clips provided courtesy of Professor Patricia Reiff, Rice University Connections Program

Visit the Space Weather section to learn more about the aurora

Last modified prior to September, 2000 by the Windows Team

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