Navis.gr - The 'Aurora Borealis' Show

Aurora Borealis One of the greatest natural light shows on Earth is the Aurora Borealis (Northern Lights). The best place to see it is near the Arctic Circle in Scandinavia, Canada or Alaska at Spring equinox.

Click on the Aurora Image to Watch the 'Aurora Show'

See also the 'Dancing Northern Lights' animation [105 KB]

An aurora is a display of coloured light in the night sky that occurs primarily in high latitudes of both hemispheres. Auroras in the Northern Hemisphere are called the northern lights, or aurora borealis. In the Southern Hemisphere auroras are called the southern lights, or aurora australis.

The aurora is usually white with a greenish tinge but may take on a yellowish or reddish cast. Vertical rays, like searchlight beams, are common. In the beautiful corona form of aurora, rays seem to meet overhead in a starlike shape. In the spectacular flame type, tonguelike rays ripple upward. Vertical rays rising from curving bands are called draperies.

Auroras appear when highly charged particles from sunspots and solar flares excite the thin gases of the upper atmosphere and make them glow. Displays are most frequent in spring and fall because the Earth is then most nearly in line with zones of the sun where sunspots are large and frequent. However, auroras may be most frequent during winter in certain areas.

The particles from the sun are deflected by the Earth's magnetic field toward the geomagnetic poles. (These poles mark the axis of the Earth's magnetic field and are not the same as the magnetic poles, which mark points at which lines of magnetic force are vertical.) The particles then collide with oxygen and nitrogen atoms, knocking away electrons to leave ions in excited states. These ions emit radiation at various wavelengths, creating the colours of the aurora.

In the spring of 1989, astronomers across the Northern Hemisphere as far south as southern California (Perspective View [43 KB]), Florida, and Arizona observed a series of spectacular auroras. Especially prominent were the auroras observed in the months of March (auroras which appeared unusually red) and May (auroras which consisted of arcs, rays, and sheets of greenish light).