THE AURORA: FIRE IN THE SKY...The northern lights (or the southern lights, if you’re from the Southern Hemisphere) are eerie, multicolored streaks and shapes that appear in the night

COLORS IN THE NIGHT SKY: THE AURORA COLORS IN THE NIGHT SKY: THE AURORA

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Birkeland had an idea. He knew that Earth was a giant magnet. Like all magnets, Earth has a north magnetic pole and a south magnetic pole. Birkeland led an expedition to Norway to measure Earth’s magnetic field.

He found that near the North Pole, the magnetic field lines don’t run along the Earth’s surface, the way they do near the equator. Instead, the field lines go almost straight up and down. What could that mean?

Think of the Earth as a magnet. Near the middle of the magnet (where the Earth’s equator would be) the lines of force run right alongside the magnet. But near the North and South Poles, the lines run almost straight into the ends of the magnet.

THE AURORA: FIRE IN THE SKYBY STEPHEN WHITT

MAY 2008

Earth’s magnetic field. Illustration courtesy of Wikimedia Commons.

http://beyondpenguins.nsdl.org

Issue 3: Polar Patterns: Day, Night, and Seasons (May 2008)Copyright February 2009 – The Ohio State University

ABOUT THE AUTHOR

Stephen Whitt

Director of Experience Programs Teaching and Learning COSI

Supported by the National Science Foundation

Licensed Under a Creative Commons license.

http://creativecommons.org/licenses/by-sa/3.0/

Find this story and others at:http://beyondpenguins.nsdl.org/information.php?topic=stories

Flesch - Kincaid RL = 5.2

Stephen Whitt has been with COSI since 1993, performing shows and demonstrations, writing exhibit signs and show scripts, and co-directing COSI’s f loor faculty. He has written over 40 articles for children’s science magazines, and his first book, called The Turtle and the Universe was published by Prometheus Books in 2008.



What happens when you reach Earth? To find out, let’s leave the solar wind for a moment and travel back in time, to meet a scientist and explorer named Kristian Birkeland.

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Before the charged particles can get to the ground, though, they smash into air molecules. The collisions make the molecules glow with beautiful, bright colors – green, pink, and red. This is the aurora, light created by tiny particles from the Sun smashing into the Earth’s atmosphere at the end of a four-day journey through space. That’s quite a trip!

Imagine you are on the Sun. The Sun’s temperature is much too hot for anything alive. But you aren’t alive. You are a tiny particle so small that you can’t be seen in even the most powerful microscope.

Have you ever rubbed your feet across the carpet and then touched something made of metal? If you have, you’ve felt a shock! You build up an electric charge when you rub your feet on the carpet. The charge moves from your finger to the metal when you touch it. This movement is what causes the shock.

The particles from the Sun also carry an electric charge. But how does this charge create the aurora?

Sun’s surface. Photo courtesy of NASA.

Aurora Australis captured by NASA’s Image Satelllite. Photo courtesy of NASA.

Kristian Birkeland. Photo courtesy of Wikimedia Commons.

The northern lights (or the southern lights, if you’re from the Southern Hemisphere) are eerie, multicolored streaks and shapes that appear in the night sky, as if from nowhere. To find out where they come from, we’ll have to take a little trip. Are you ready?

Kristian Birkeland now knew more about the Earth’s magnetic field. But he still didn’t know what caused the aurora. How were the two things related?

To understand how these things are related, you need to know a little

about electricity.

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Kristian Birkeland wanted to understand the aurora (another name for the northern and southern lights). The mysterious light was often seen near the North and South Poles. It wasn’t usually seen closer to the equator. People described the light as a “fire in the sky.” But what could it be?

aurora - another name for the northern or southern lights.

compass - a tool that measures Earth’s magnetic field and is used to find directions.

electric charge - a measure of the extra positive or negative particles that an object has.

expedition - a trip made by a group of people for a particular purpose.

magnetic field - the space all around a magnet where the force of the magnet can act.

particles - tiny pieces of matter that make up solids, liquids, and gases.

molecules - a grouping of two or more atoms joined together.

solar wind - electrically charged particles that come from the sun.

GLOSSARY



Photo courtesy of Rhys Boulton, U.S. Antarctic Program, National Science Foundation. Penguin icon courtesy of iconfinder.com.

The Aurora Borealis, or Northern Lights, shines above Bear Lake. Photo courtesy of Joshua

Strang, U.S. Air Force, Wikimedia Commons.

Northern Lights. Photo courtesy of stock.xchng.

Here’s the key idea. Electricity and magnets affect each other. Watch a compass during a thunderstorm. You’ll see the magnet inside the compass (what we call the needle) move every time lightning f lashes

across the sky.

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Now we know that electricity affects magnets. But do magnets affect electricity? Yes! Kristian Birkeland showed how by building a magnetic model of the Earth. He found that the charged particles traveled along the magnetic field lines. They moved away from the equator and followed the lines to the North and South Poles.

Now let’s go back to those real charged particles flying off the Sun. Just like in the model, the charged particles are pushed by the Earth’s magnetic field toward the poles. Once they get there, they follow the magnetic field lines down toward the ground.

Now imagine that you are hurled away from the Sun. Believe it or not, this actually happens all the time. The Sun sends out streams of tiny particles every second. We call this stream the solar wind.

Solar Wind. Illustration courtesyof Image Editor, Flickr.

Heat causes the solar wind. The Sun is so hot that particles f ly off its surface, a little like steam rising from a hot bowl of soup.

Imagine you’re a part of this solar wind. You’re f lying away from the Sun faster than the fastest spaceship. Directly ahead of you is Earth, a pretty blue-white ball. You’re moving fast, but Earth is still far away. It takes you a little over four days to make the trip to Earth.



Photo courtesy of Wikimedia Commons. Icon courtesy of iconfinder.com.

Earth. Photo courtesy of NASA, Goddard Space Flight Center.

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THE AURORA: FIRE IN THE SKY...The northern lights (or the southern lights, if you’re from the Southern Hemisphere) are eerie, multicolored streaks and shapes that appear in the night