Here is another image of the southern aurora taken from the Space Shuttle. The aurora changes with time, often looking like moving curtains of light. Here are some MPEG and QuickTime film clips that illustrate the time dependence of the auroral display.

The Cause of Auroras

Auroras are caused by high energy particles from the solar wind that are trapped in the Earth's magnetic field. As these particles spiral back and forth along the magnetic field lines, they come down into the atmosphere near the north and south magnetic poles where the magnetic field lines disappear into the body of the Earth.

The delicate colors are caused by energetic electrons colliding with oxygen and nitrogen molecules in the atmosphere. This excites the molecules, and when they decay from the excited states they emit the light that we see in the aurora.