Aurora's brightness can vary from the faintest hints of the Milky Way to an illumination bright enough to cast shadows and change snow cover to a vivid green! Its structure can go from a diffuse homogeneous glow to one with discrete sharp boundaries and complex internal structure known as rays that zip across the sky in seconds. Its color, which is mostly green, can have red bottoms or tops or be entirely pink or red. Purple aurora results from the tops of the displays that are lit by the sun (which is well below the horizon). Unlike clouds, most stars will be visible through all but the brightest aurora.

While aurora is most frequent around local midnight, it can be viewed when the sun is 12 degrees below the horizon or lower. Generally, aurora starts in the East as a uniform smooth diffuse arc from horizon to horizon and as the night progresses, it rises and forms a discrete band that is irregular and filled with slightly converging brighter areas known as rays. As the display brightens, these bands will begin to fold onto themselves and form a curtain or drapery formation. If the display continues to intensify, the rays will converge to a vanishing point at the magnetic zenith (nearly overhead in Alaska) and form a corona. These displays are pretty rare and a definite trophy to the patient photographer. After the display dies down (sub-storm passes), a general glow or patchiness will persist across most of the sky and a strobing or pulsating effect between 0.1 second to 30 seconds in duration will be seen. The display cycle can always repeat itself over and over during the remainder of the night, so don't quit looking. Evening aurora move from east to west and reverse direction after midnight.