photo credit: Lars Poort, Greenland
An aurora is a wavering glow of light that is seen sometimes in the night sky in the direction of the North or South poles. The ones we see in the Northern Hemisphere are sometimes also called the northern lights.
An aurora is caused by very fast, charged particles—mostly electrons—that came from the Sun. Because of the earth’s magnetic field, these are partially deflected so that they come into our atmosphere toward the North and South poles. When nitrogen molecules of our air are hit by those fast particles, they become very excited molecules.
They become ordinary molecules again by giving off energy as light. That gives the faint wavering glow we call an aurora.
Thanks to Science Question for this explanation.
Use this Aurora Observing Guide to find out about different auroras. (Downloadable Word document for use in schools)
Thanks to Lars Poort, in Greenland, for this guide to aurora observing.
Even if you don't live at a high latitude (very north or south) where auroras are commonly seen, you can learn about auroras with just a bar magnet and map of the world! Thanks to Sandy Zicus for the following activity:
You can demonstrate the Earth’s magnetic field, and then see where auroras are most likely to occur, by doing the activity below.
• 1 large bar magnet
• picture of globe printed on a fairly rigid sheet of paper or clear plastic
• iron filings
1. Place the picture of the globe on top of a large bar magnet, with the poles of the magnet tilted about 11º from the geographic poles on the globe. This represents the location of the Earth’s magnetic poles.
2. Sprinkle some iron filings on the plastic or paper and tap it gently. You should be able to see that the iron filings arrange themselves in pattern around the magnet forming closed lines that represent the magnetic field.
photo: Thomas Spiess