The Aurora Borealis is the name given to the extraordinary display of lights in the atmosphere near the Arctic Circle. Also called the “Northern Lights,” the Aurora Borealis form spectacular colors and clouds shapes that appear to dance and move in the sky. The Aurora Borealis has been noted since ancient times and many myths arose around its occurrence. The colored lights also display around the South Pole, where they are called the “Aurora Australis.” Borealis and Australis correspond to the words “north” and “south.”
What Exactly Is the Aurora Borealis?
Since early times, people have noted the luminous glow of multi-colored lights that dance in the sky in Polar Regions. These lights appear in bands that streak across the sky and move in peaks and oscillations. The intensity of this dancing light varies from year to year and seems to peak every 11 years.
What Causes the Aurora Borealis?
The Aurora Borealis is an atmospheric display of colors in the sky that occurs when atoms and molecules become excited. This excitation is now known to be caused by solar winds that are blown to the Earth. When the winds reach the Earth’s atmosphere, they pass along magnetic fields, causing electrons to become excited. The charged particles collide with oxygen and nitrogen atoms, and as the energy is released, the colors appear. Aurora displays occur more frequently during time of sunspot activity. The displays can reach over 600 miles in height. Auroras are best seen in winter at the darkest point of night.
Forms of Aurora Displays
This release of energy can cause rippling curtains, pulsating blobs and pulsating streams or heavy glows. The curtain effect appears as the charged particles move parallel to the natural lines of the magnetic field. Three dominant forms are generally seen. The first form is a homogenous band or arc rising low in the sky. In the second form, vertical rays stream up from the band like a fringe. The third form, called a corona, can be seen when the aurora is directly above you, as the rays fall around you from a high point in the sky. These forms can mix and changes rapidly depending on environmental conditions.
What Makes the Color in the Aurora Borealis?
Color is emitted when the excited atoms and molecules release energy as they drop into a more normal state. The composition of the atmosphere, its density and the altitude where it occurs determines the light emissions that occur. The oxygen molecules create the greenish glow. Ionized nitrogen causes a blue or purplish color. Neutral nitrogen causes a yellow or orange-ish glow. The altitude where these atoms are found can also affect the color display.
