My First Aurora Borealis

Friday night, I saw my first aurora borealis. It looked a lot like this:

It was pretty faint, but definitely there and extraordinarily beautiful and even though it only lasted maybe 40 minutes, I stayed up all night watching the sky. If I wasn’t already an astro nerd, I would definitely be one now. If you ever have an opportunity to see the aurora, no matter how late you have to stay up, do it. Spaceweather.com has a good auroral oval on the left side of their page which is constantly updating. If the red and orange parts are over where you are, you might be able to see the aurora. The more orange-y it is, the more it’ll look like what I saw. But, if you’re farther north, you could see it like any of these:

File:Aurora Borealis Poster.jpg

Photograph from WikiCommons

Anyway, since then I’ve had a few people ask me to explain how the aurora works. I found that I couldn’t explain it in much detail, so I did some research and here is a better explanation:

It all starts with a solar wind. The sun is constantly shooting out charged particles (protons and electrons) in all directions. This constant stream of particles is called the solar wind. A lot of the time, the solar wind is fairly calm and constant, so there is no visible aurora. However, every once in a while there is essentially a storm on the sun, sending flares of charged particles towards Earth. It’s the nature of charged particles to follow magnetic fields, and Earth has quite a large magnetic field. So, the charged particles follow the magnetic field of the earth to the North and South poles. The poles aren’t called that by accident – if you imagine the earth as a huge bar magnet, the poles would be the ends of that bar magnet, and the magnetic field of the Earth lead straight into the poles, directing the charged particles from the solar wind there. That’s why you can only see the aurora from very northerly or southerly areas.

As the charged particles follow the magnetic field down toward the surface of Earth, they start to smash into the particles that make up our atmosphere, adding energy to those particles which is then released again as light. That light is the aurora. The intensity of the aurora depends on what the magnetic and electric fields around Earth are doing (they’re constantly changing – this causes the aurora to appear to shimmer and dance), as well as the amount of charged particles being sent into the atmosphere. The color of the aurora depends on what kind of particles the solar wind is smashing into: our atmosphere is made up of mostly oxygen and nitrogen. Oxygen releases green or reddish light, whereas nitrogen releases blue or purple light.

So. Recap. Auroras happen when solar winds send out charged particles. Those charged particles follow Earth’s magnetic field and smash into the atmosphere’s oxygen and nitrogen, causing them to gain energy and then release it as light. That light is the aurora. When there is a stronger solar wind due to storms on the sun, the aurora is brighter and visible farther from the poles. The aurora is awesome in both the new and old sense of the word. It’s another one of those huge phenomena that really reminds me how small we are down here.

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One thought on “My First Aurora Borealis

  1. Pingback: People Learn. | Down Here on Earth

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