Who Turned on the Lights?
Two For the Price of One
First of all, there are two sets of these dancing rainbow lights: the aurora borealis of the Northern Hemisphere and the aurora australis of the Southern Hemisphere. We here in the U.S. hear more about the Northern Lights, but folks below the equator are more likely to hear about the Southern Lights. In either case, however, they are caused by an interaction of magnetically charged particles from the sun interacting with molecules of air on earth. The result? A beautiful display of rainbow colors that appear as shifting bands, rays, draped web-like shapes, or even arcs which look the most like rainbows.
Solar Flares
On average, about every 10 to 11 years, gases exploding out from the sun's surface cause the emission of negatively and postively charged protons. The blast of the flare is so powerful, a "solar wind" is created which carries the particles toward the earth. Once there, these particles are drawn toward the magnetic fields at the earth's north and south poles. It is here, at between 60 and 200 miles above the earth, that the colors begin to dance. Depending upon the power of the solar flares, the earth's magnetic field is more or less distorted and with the distortion comes a spreading of the lights, possibly being seen as far south as Mexico.
But even when the flares are not blue ribbon winners, there is still enough behind the sun's expulsions to create the lights about 240 nights each year. The Northern Lights are most often seen across the northern portion of the planet (hence the name) across Norway, northern Siberia and part of Alaska.
It's a Chemical Thing, Dude
Why all the colors? Well, when those charged particles from the sun collide with the molecules and atoms in our air, it's a tiny 4th of July celebration. Depending on the type of molecule or atom involved, you might see red or green (the glow from hydrogen or oxygen), and if you see pink or purple, you're looking at nitrogen pyrotechnics. And this display won't stand still, so don't get confused by somebody's neon sign at the local restaurant, or street lights. These lights shift color, bounce around, grow dim and then suddenly brighten, and generally put on quite a show. Of course, cloud cover makes them pretty much impossible to view, and it may be difficult or impossible to see them in town where the city lights keep us from even seeing many stars in our sky.
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