The Aurora Borealis or Northern Lights are mesmerizing, dynamic displays of light that appear in the nighttime Arctic skies. They are, in effect, nature's light show; visual poetry penned from the quantum leaps of atmospheric gases. As those who have witnessed the Aurora can attest, few sights can equal the magic and mystery of these luminous sheets of color undulating in the frigid air of an Arctic night.
Although auroras appear in many forms -- pillars, streaks, wisps and haloes of vibrating color -- they're most memorable when they take the form of pale curtains which seem to float on a breeze of light. Known as 'Aurora australis' in the south, auroras occur in the upper atmosphere of both poles and are occasionally visible from middle latitudes as a dark red glow near the poleward horizon. They are most commonly seen at midnight hours in the north in a circle including southern Hudson Bay, southernmost Greenland, Iceland, the northern tip of the Scandinavian peninsula, the Arctic coast of Siberia, and central Alaska.
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 gases in the upper atmosphere. These collisions produce electrical discharges which energize atoms of oxygen and nitrogen causing the release of various colors of light. Earth's magnetic field channels these discharges toward the poles. Variations in sunspot activity or the occurrence of so-called 'coronal holes' can often considerably enhance the auroral discharge adding to the intensity and duration of the displays.
Auroral displays appear in many colors with pale green and pink the most common. However, different shades of red, yellow, green, blue, and violet have all been observed. Green results from energized oxygen atoms and pink from nitrogen molecules. The color variations are a product of the altitude of the storm, and the density and composition of the ions at that altitude. The folding effect results from the electric field induced on either side of the auroral curtain by the electrons.
Inidigenous peoples have many different myths to explain the Aurora Borealis. The Inuit, for example, attach spiritual significance to the lights, believing them to represent the souls of their unborn children or the torches of long-departed ancestors. In Middle-Age Europe, the northern lights were thought to be reflections of slain warriors battling valiantly in the heavenly skies for eternity.