Auroras are natural light displays that occur high in the atmosphere. The solar wind, a stream of charged particles ejected by storms on the sun’s surface, is attracted by the earth’s magnetic field. These particles strike oxygen and nitrogen atoms as they accelerate toward earth’s magnetic poles. These collisions release energy as variously colored light. These displays usually occur in high latitude bands circling the earth near either magnetic pole. An aurora in the northern hemisphere is called the aurora borealis, whereas one in the southern hemisphere is referred to as the aurora australis. These names are derived from Latin. Aurora means sunrise, and was the ancient Roman goddess of the dawn, while borealis and australis signify north and south.
Most often seen in the Arctic and Antarctic, auroras sometimes appear over northern areas of Scandinavia, North America, and Asia and in the southern areas of South America, New Zealand, and Australia. At times, however, unusually massive ejections of material from the sun make auroras visible over far larger areas. The Carrington Event, one of the largest solar ejections ever documented, caused the aurora seen over Tuscaloosa and much of the world in 1859.
Almost 13 years later, on Sunday night, Feb. 4, 1872, the aurora borealis made another rare southern appearance in “glorious magnificence.” A crimson band 20 times the width of the full moon extended from overhead to the eastern horizon. An unnamed young woman wrote in The Tuscaloosa Times that, “At times it seemed a vast pyramid of luminous matter, then rapidly changing in shape and brilliancy, it assumed the appearance of an inverted cone of dull electric light…It was a bright red, brighter in the East and varying in intensity until it reached the northwest, where it became a vague, diffusive light…”
In more recent times, Tuscaloosans witnessed other manifestations of the aurora borealis. In September 1941, what was at first believed to be neon signs reflecting off clouds turned out to be the northern lights. Because auroras can induce electrical currents in electronic equipment, communications suffered worldwide disruption. In March 1989, a large solar storm generated an aurora seen over most of Alabama. In March 1991, an aurora appeared as far south as Andalusia and into the Gulf of Mexico. More recently, in November 1991, the aurora borealis extended over Alabama and Georgia.
Ancient and medieval people considered auroras to be supernatural manifestations. Some saw them as spirits of the dead or signs from God. In recent times, researchers have developed rational scientific explanations for these lights in the sky. Astronauts have even made striking videos and taken photographs looking down upon auroras from the International Space Station. However, people still visit the far northern or southern regions, or eagerly anticipate rare appearances in other areas, for one of nature’s most awe-inspiring sights.
Suggested additional viewing:
British physicist Dr. Les Cowley maintains a website with images of auroras and other aerial phenomena at atoptics.co.uk.
Numerous photographs and videos of auroras are also available on other internet sites such as nasa.gov.