Tanya Needles, age 12, of High Point, N.C., for her question:
WHAT ARE NORTHERN LIGHTS?
In March and April in the spring and again in September and October in the fall, many people in certain parts of North America are able to see a glowing or flickering of natural light at night in a great show called the northern lights. A similar display is seen in the Southern Hemisphere and is called the aurora australis.
The northen lights are also called the aurora borealis.
Scientists say that an aurora borealis takes place when protons and electrons are shot from the sun, striking the earth's upper atmosphere. The earth's magnetic field then directs the particles toward the magnetic poles. They collide with atmospheric particles as they move, and then they change their electrical charge. They glow much like the charged particles in a fluorescent tube.
The aurora borealis happens most frequently in the far northern regions, although beautiful displays of lights have been seen in many parts of the northern United States and even as far south as Mexico.
An auroral display will usually happen about 70 miles above the earth's surface. At times it will take place at about 150 miles high.
There are actually many different kinds of auroral displays. Some extend in an arc for hundreds of miles. At other times thin, long rays form what appear to be actual curtains of light.
The most common color seen in aurora borealis displays is green, caused by atomic oxygen. The color red is also seen frequently, and this is caused by molecular oxygen and by nitrogen. Frost white beams and ever changing hues are also seen regularly as the lights seem to move with the breezes.
Auroral displays seem to happen most frequently when there is a period of great sunspot activity. Sunspots definitely affect the zone in which the displays occur. The zone shifts toward the equator at the time of maximum sunspot frequency, and toward the poles when the sunspots are at a minimum.
Northern lights displays also seem to be associated with magnetic storms.
The word aurora comes from the goddess of dawn in Roman mythology who opened the gates of heaven for the sun god every morning. Dewdrops you find on the grass some mornings are said to be tears shed by Aurora over the loss of her son Memon who was killed at Troy. She is, mythology also says, the mother of the winds.