|
||||||
|
|
||||||
 |
 |
|
Basics
|
Also called the northern lights, the spectacular color displays of the aurora borealis appear on clear, cold nights in the arctic sky during periods of solar activity. The aurora borealis is centered around the geomagnetic North Pole, but displays may be observed up to 5000 kilometers away. The height of the auroras is about 70 kilometers to 200 kilometers above the earth's surface.
The amazing color displays and formations are produced by the solar wind, a stream of electrons and protons coming from the sun, as it collides with oxygen and nitrogen atoms in the upper atmosphere. High-altitude oxygen, about 200 kilometers up, produces rare, all-red auroras, while lower-altitude oxygen, about 60 kilometers up, is the source of the most common auroral color, a bright yellow-green. Blue light comes from ionized nitrogen molecules. The nitrogens also create purplish-red and red colors in the aurora.
The following images are some examples of auroral activity:
 Auroral Arc |
 Corona Formation |
 Curtain with Rays |
 Multi-Colored Bands |
 High Altitude Aurora |
 Twilight Display |
Photographs courtesy of Jan Curtis (1998,1999)
