An aurora happens when energetic electrically charged particles, like electrons, collide with atoms of gas as they accelerate along the Earth’s magnetic field lines in the upper atmosphere.
Those collisions cause the atoms to give off light. Auroras are a lot like neon signs, except that the conducting gas is in the Earth’s ionosphere instead of inside a glass tube.
Frequently Asked Questions about Auroras
If you don’t find your answer here, you might try the FAQ at Poker Flat, or the Asahi Aurora Classroom. For even more in-depth information, I recommend David Stern’s educational files. A very nice and in-depth website with lots of animations is the COMET program at HAO (free, but registration is required). A good book (it’s hard to put web pages on a shelf…) that I recommend is “The Aurora Watcher’s Handbook” by Neil Davis.
Links to real-time geophysical data that are related to the aurora and aurora forecast can be found at University of Alaska Fairbanks. Links to websites with auroral photography and information are NASA, Aurora Service EU, Alaska Photographics, more links here, Michigan Tech & at Aurora Notify.
A luminous atmospheric phenomenon appearing as streamers or bands of light sometimes visible in the night sky in northern or southern regions of the earth. It is thought to be caused by charged particles from the sun entering the earth’s magnetic field and stimulating molecules in the atmosphere.
One thing is the air we breathe, our atmosphere. It is really a mixture of several gasses, mostly nitrogen and oxygen, with traces of hydrogen, helium and various compounds.
A Field of Earth
Another thing we can’t see is a magnetic field that surrounds the Earth. If you’ve ever played with a bar magnet and iron filings you’ve seen the curved patterns the filings form in the magnetic field. The next picture shows how the magnetic field around the earth’s core is like the field of a bar magnet.
This wind is always pushing on the Earth’s magnetic field, changing its shape. You change the shape of a soap bubble in a similar way when you blow on its surface. We call this compressed field around the earth the magnetosphere. The Earth’s field is compressed on the day side, where the solar wind flows over it. It is also stretched into a long tail like the wake of a ship, which is called the magnetotail, and points away from the Sun
Squeezing the Earth’s magnetic field takes energy, just the way it takes energy to compress a balloon with air in it. The whole process is still not fully understood, but energy from the solar wind is constantly building up in the magnetosphere, and this energy is what powers Auroras: (a full story)
Can I see them anywhere?
Yes. Although more frequent at higher latitudes, closer to the poles (such as in Canada, Alaska, Antarctica), they have been seen closer to the equator as far south as Mexico. To view them, look in the direction of the closest pole (the northern horizon in the northern hemisphere, the southern horizon in the southern hemisphere).
Can I see them at any time of the year?
Yes. In some areas, such as Alaska or Greenland, they may be visible most nights of the year. And they occur at any time of the day, but we can’t see them with the naked eye unless it’s dark.
What causes the colors and patterns?
Colors and patterns are from the types of ions or atoms being energized as they collide with the atmosphere and are affected by lines of magnetic force. Displays may take many forms, including rippling curtains, pulsating globs, traveling pulses, or steady glows. Altitude affects the colors. Blue violet/reds occur below 60 miles (100 km), with bright green strongest between 60-150 miles (100-240 km). Above 150 miles (240 km) ruby reds appear.
- A wonderful Arctic Website (Aqua Firma)
- Aurora lecture on channel 15 (auroranotify.com)
- Aurora Hunter (Website and Knowledge base)
- Unfurled aurora (blogs.discovermagazine.com)
- Aurora (Wikipedia)
- Aurora Pictures: Best Fall Photos of Northern Lights (news.nationalgeographic.com)