"The Aurora Borealis"
Teagan Calahan, Undergraduate Geographer/EIUWC Weather Analyst/WEIU Skywatch Forecaster
February 3, 2012
The northern lights, scientifically known as aurora borealis if you in the northern hemisphere, and aurora austrailias if you’re in the southern. For centuries these enchanting lights have captivated people’s attention and wonder. Back in Roman times there were myths that the lights were the appearance of the goddess of dawn, Aurora. During medieval times people saw them as a warning of oncoming war and/or famine. The Moari of New Zealand believed that the lights were simply reflections of torches of campfires. Obviously today we know that none of these beliefs are true, the sighting of the northern lights are a little more complicated.
The northern lights begin with the sun. Protons and electrons from the surface of the sun are blown into the earth’s atmosphere by solar wind. When the sun’s charged particles reach the earth’s atmosphere they collide with earth’s charged particles, creating the northern lights. The lights that are seen do not always look the same, they are often seen in patches, scattered clouds of light, streamers, arcs, rippling curtains or shooting rays. The lights are also not always the same color; depending on what gas particles collide the northern lights can be a variety of different colors. For example, when the sun’s particles collide with oxygen molecules, it creates the pale yellow- green color that is most often seen (figure 1). Colliding with nitrogen creates a blue-purple color in the sky, and when oxygen molecules at higher latitudes collide, it creates a rare all-red color.
It is believed that when the aurora borealis occurs it acts like a mirror image in the north and south poles, with almost the same pattern and color happening as the same time. Since it is seen at the magnetic poles, the northern lights can sometimes be seen as far south as New Orleans, even when seen this far south people west or east are not able to see them. As far as predicting the northern lights, it is plausible that when there is a strong solar wind that there will be a strong display, but often we cannot notice a change in the wind until a couple of hours before the show begins.
Figure 1. Green aurora borealis. Photo from NOAA.