Astronomy

Aurora Borealis the Northern Lights



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Why Are Northern Lights Northern?

One of the most beautiful sights in nature has got to be the northern lights, The Aurora Borealis. These vague curtains of light shift, drift and flash in and out of the night sky of the far North in a display as breathtaking as it is ephemeral. Why just the North? Why on a cold winter's night in Kansas can I not look into the sky and see the lights?

First and second of all, it's not just the North and you can see them sometimes in Kansas. To understand why you have to understand what the Northern Lights are and how they are formed.

The simplest explanation for the Northern Lights is that they are a florescent light without the tube. Charged particles from the sun enter the Earth's atmosphere just as electricity travels down the tube of a florescent bulb. There it interacts with molecules high in the sky causing them to glow just like the neon in the bulb.

The Earth is generally protected from such high energy particles by a circling stream of radiation called the Van Allen Belts. These are generated deep inside the Earth by the movement of its molten core. They range around the planet like the magnetic lines around a bar magnet. Energetic particles that strike them don't go directly through to the atmosphere. They are moved along the Belts until they reach the points where the lines drop back into the Earth; the North and South poles. So the answer to the first question is; northern lights are actually northern and southern lights and can be seen dancing over Antarctica as well.

As for why you can't see them in Kansas, or anywhere else mid-latitude, we've partly answered that already. The Van Allen Belt diverts the energy to the poles. Still, you can sometimes see them. As the radiation enters the atmosphere it spreads out, up and down from the poles, around the globe. It continues to spread until it burns all its energy. Usually this happens while the Aurora is still far in the North. In the case of solar storms, it is possible for the entire sky of the Earth to be lit at night. The last documented sighting of the Northern Lights in Kansas was in 2003 when a particularly fierce solar storm washed over Earth. Even then the event was only confirmed in a few locations in the Northern part of the state.

Northern Lights, not so northern after all.

References:

www.wikipedia.com

www.washburn.edu

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