Astronomy Question: Understanding Aurorae
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Image of “Southern” lights (Aurora Australis) Taken by STS-39 crew. Image Credit: NASA/JSC
Azmaria asks,
Dear Astronomer, I know that there’s a link between solar flares, the poles, and the upper atmosphere to make auroras, but what exactly is that link?
Why are they so much more beautiful from space, and why are they normally green?
Great question Azmaria!
Aurorae ( or Auroras ) have been in the news quite frequently, partly due to some very powerful solar outbursts this year.
Let’s explore how particles from our sun interact with Earth’s magnetic field and upper atmosphere to produce these wonderful phenomenon.
Starting with the solar wind, solar flares, and Coronal Mass Ejections, charged particles ( electrons and protons ) can be hurled from the sun at speeds of nearly 800 km/sec! The charged particles fly through space and interact with Earth’s magnetic field, and upper atmosphere.
Regarding why Aurorae are more impressive from space, I would have to say for the same reasons why the Hubble Space Telescope works well in space – less interference from our atmosphere ( moisture, wind, dust, smog, etc ). As for the colors present in an Aurora, it’s simple chemistry/physics!
When an atom is excited ( receives energy ) it can return to its “ground” state by emitting light in the form of photons. Since Earth’s atmosphere is mostly Oxygen and Nitrogen the dominant colors in an Aurora would be reds/greens (Oxygen) and blues/reds (Nitrogen).
If you are lucky enough to be within 20° (sometimes farther during an intense solar outburst) from the North or South magnetic poles, you’ve probably been able to see the tell-tale hazy green, blue, or red ribbons in the sky that mark to occurrence of an Aurora.
Read more about solar storms at NASA’s Solar and Heliospheric Observatory (SOHO) homepage at: http://sohowww.nascom.nasa.gov/
Ray Sanders is a Sci-Fi geek, astronomer and blogger. Currently researching variable stars at Arizona State University, he writes for Universe Today, The Planetary Society blog, and his own blog, Dear Astronomer
2012-12-04 08:06:49
Source: http://www.dearastronomer.com/2011/11/02/astronomy-question-understanding-aurorae/
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