Were those the Northern Lights last Tuesday?

Yes! If you were out late on Tuesday night, you might have seen the Northern Lights. The Northern Lights, also called aurora borealis, appear as a diffuse glow or as overlapping curtains of greenish-white and sometimes red light in the night sky.

Auroras are triggered when the sun ejects a cloud of gas, called a coronal mass ejection. It takes two to three days for the charged particles in this gas to reach Earth. Earth’s magnetic field deflects these particles toward the North and South poles. When these charged particles collide with a molecule or an atom, they can excite the molecule, increasing its energy state. When these molecules or atoms shift back down to their normal energy states, they emit light.

Auroras form between 60 and 250 miles above the Earth’s surface when these charged solar particles collide with two abundant constituents of our atmosphere: nitrogen and oxygen. The interaction of the charged particles with nitrogen molecules results in pinkish or magenta light, while oxygen atoms emit greenish light. A majority of the collisions occur near the poles, so the Northern Lights are usually seen at the higher latitudes of Canada and Alaska. When a large number of particles are emitted by the sun, which usually happens after a solar flare, the lights from the collisions can be seen throughout Wisconsin and other northern states.

Our sun goes through active and quiet energy cycles. The time between 2008 and 2010 was a very quiet time for the sun, and now the sun is in an active stage, providing opportunities to see more of these great natural light shows during cloud-free nights.

Category: Phenomena

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