Basic Facts About the Aurora

What Causes the Auroral Lights?

High speed ions and electrons travel along magnetic field lines and impact the atmosphere in the region called the auroral oval. Atmospheric gases are excited by these high speed collisions and give off different types of light as they relax back to their normal states. The color and altitude of the aurora tell us which atmospheric gases are being excited.

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

Since blue, green and red light are being produced in various combinations at various altitudes, it mixes to give an incredible variety of colors (such as purple and pink).
Movie adapted from original clips provided courtesy of Professor Patricia Reiff, Rice University Connections Program.



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