Auroras: What makes them happen?

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. 

Norway 2012
Norway 2012, by Bjørn Jørgensen.

Frequently Asked Questions about Auroras

aurora australis from space
Aurora Australis from Space

University of Alaska ~ Geophysical Institute

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.

Aurora jpg
North Sky in Ersfjordbotn, Troms Fylke, Norway

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 Photographicsmore links here, Michigan Tech & at Aurora Notify.

Green Aurora
Aurora Australis via chiefscientist.gov.au (image links)
  1. What is an aurora?
  2. What makes the color of the aurora?
  3. What is the altitude of aurora?
  4. What causes the aurora?
  5. Why does aurora have the shape of curtains?
  6. How often is there an aurora?
  7. Where is the best What place to see aurora? And what time is best?
  8. Do auroras occur on other planets? If so, which other planets?
  9. Can you hear the aurora?
  10. Are there auroral displays around the South Pole? How are they different?
  11. What is a proton aurora?
  12. What is a black aurora?
  13. Can you predict when and where there will be aurora?
  14. Does the aurora have any effect on the environment?

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.

Auroras: What makes them happen?

Before we can understand auroras, we need a few facts about the space around our Earth. There are many things in this space that we can’t see.

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.

Aurora via NASA
Via NASA

 

aurora australis
Aurora Australis (Southern Hemisphere) NZ, by Liz Carlson

 

Aurora Australis
Tim Gard Photography image of the Aurora Australis in Australia

~*~

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

Earth's magnetosphere in the solar wind

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.

EIELSON AIR FORCE BASE, Alaska -- The Aurora Borealis, or Northern Lights, shines above Bear Lake here Jan. 18. The lights are the result of solar particles colliding with gases in Earth's atmosphere. Early Eskimos and Indians believed different legends about the Northern Lights, such as they were the souls of animals dancing in the sky or the souls of fallen enemies trying to rise again. (U.S. Air Force photo by Senior Airman Joshua Strang)
EIELSON AIR FORCE BASE, Alaska — The Aurora Borealis, or Northern Lights, shines above Bear Lake here Jan. 18. The lights are the result of solar particles colliding with gases in Earth’s atmosphere. Early Eskimos and Indians believed different legends about the Northern Lights, such as they were the souls of animals dancing in the sky or the souls of fallen enemies trying to rise again. (U.S. Air Force photo by Senior Airman Joshua Strang)

White Northern Lights, Finland
White Northern Lights, Finland
Aurora
Reykjavik City, Iceland. by arctic-images.com/ljosid/ (image linked)

aurora infographic

Related articles

Aurora during a geomagnetic storm that was mos...
Aurora during a geomagnetic storm that was most likely caused by a coronal mass ejection from the Sun on 24 May 2010. Taken from the ISS. (Photo credit: Wikipedia)
Advertisements

17 thoughts on “Auroras: What makes them happen?

  1. Oh my my … Simply awesome. The information, the music, the images, the links. Much going on here … it’s kind of an Aurora Playground! Thanks for leading me to this, and I foresee me mentioning this post in the future!

    Like

    1. Thanks! Glad you enjoyed the article! I plan to keep most of my postings updated from time to time, to help minimize the amount of them; thus making them somewhat current and informational.

      Also as Interactive as possible; With many links and yes.. Music! 😀

      Sasha

      Like

  2. Oh, dear, I reblogged so not sure how the pingback thing works. But I thought this was an interesting share for many who enjoy the lights but don’t understand the science behind them. I didn’t either. Because of my chosen name on here, I especially wanted to read and share. My name, as defined by me, means: Aurora = Light; Mo=Short for More; Realist =just that. So your piece was intriguing for more than one reason. Thanks! Happy to share 🙂

    Like

  3. Thanks Aurora! Great name to choose I too have many reasons both for my ‘afreestyler’ nickname and Sasha (name I use all the time) Nice to ‘choose’ ones own name! 🙂

    Sasha 🙂

    Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s