The Northern Lights

By Al Lowe
Contributor

Since time began, men have stared at the fantastic dancing lights in the sky, and wondered what they were. ‘Aurora borealis’ was given to the phenomenon by an Italian, Gassendi. It means ‘northern dawn’. The counter-part in the southern hemisphere is the Aurora australis.
There are a lot of things which combine to produce the northern lights. One is the earth’s magnetism. If you could stand off in space and look at this magnetic force, it would look like a gigantic doughnut, coming out of the earth at the north pole, going way out in space, and returning to the south pole. It is there all the time, and is why compasses work.
Another factor is the earth’s atmosphere. Anyway up above the earth, the gases are very thin - only a few atoms, very far apart. Oxygen, nitrogen, carbon dioxide, are all there, but in very small amounts. This is the same condition which many of you have seen in high school physics classes - gases under low pressure. The gases are usually in the little tubes, and when you put a small current of electricity through them, they light up. Oxygen is green, nitrogen bluish, hydrogen pink and so on.
A third factor is the sun. The sun emits a lot of things, including uncountable billions of electrically charged particles. These are fired through space all the time. Scientists call this the ‘solar wind’. When the sun has violent eruptions, called solar flares, a tremendous extra shower of these particles is released.
All of these things interact. The electric particles from the sun make the gas atoms light up, just as they did in the glass tubes in the physics lab. But the charged particles are trapped by the earth’s magnetism. They can’t get away, so the light appears in certain patterns in the sky.
The Aurora may just glow, or it may become a big arc high in the sky. The bands of colour can dance and wave. Sometimes huge moving clouds of colour will sweep across the sky. They can be just fantastic.
That’s not all, though. Electrical systems can be overloads because of the intense magnetic activity. Circuit breakers can be tripped, and part of an electrical grid shut down. Radio communications can be completely wiped out for days by this phenomenon. The amount of energy in the aurora is nearly equivalent to the output of all of the generators in North America.
Northern lights are always associated with activity on the sun. At times of sunspots and flares, we get bigger and better displays. Recently, there has been great activity on the sun. So keep your eye on the northern sky this winter and spring, for more astronomical spectacular.