<p>The Auroras are formed because a reconnection in the magnetic field. Particles are emitted by the Sun and collide with our magnetic field. This collision generates effects in the  ionosphere. You can read more about it in these links:</p>

<p><a href="http://www.atoptics.co.uk/highsky/auror2.htm" rel="nofollow">http://www.atoptics.co.uk/highsky/auror2.htm</a></p>

<p><a href="http://mrx.pppl.gov/Physics/physics.html" rel="nofollow">http://mrx.pppl.gov/Physics/physics.html</a></p>

CC BY-SA 3.0
2014-04-16T18:21:28.430Z
Hi dlOGO. It's discouraged to just give links in Stackexchange answers. Could you consider summarising the content of the links? Thanks.
Semidiurnal Simon
CC BY-SA 3.0
2014-04-17T03:12:50.973Z
This answer is incorrect.  The reason is not that they collide with the magnetic field (in fact, they don't, but are merely deflected by it), but they collide with the upper atmosphere.  The answer also doesn't explain how that causes visible aurorae.
gerrit
CC BY-SA 3.0
2014-04-16T16:43:32.057Z
2014-04-16T16:43:32.057Z
dIOGO
<p>Straight from <a href="https://en.wikipedia.org/wiki/Aurora#Auroral_mechanism" rel="nofollow">wikipedia</a>:</p>

<blockquote>
  <p>Auroras are associated with the solar wind, a flow of ions
  continuously flowing outward from the Sun. The Earth's magnetic field
  traps these particles, many of which travel toward the poles where
  they are accelerated toward Earth. Collisions between these ions and
  atmospheric atoms and molecules cause energy releases in the form of
  auroras appearing in large circles around the poles. Auroras are more
  frequent and brighter during the intense phase of the solar cycle when
  coronal mass ejections increase the intensity of the solar wind.</p>
  
  <p>Auroras result from emissions of photons in the Earth's upper
  atmosphere, above 80 km (50 mi), from ionized nitrogen molecules
  regaining an electron, and oxygen atoms and nitrogen molecules
  returning from an excited state to ground state. They are ionized
  or excited by the collision of solar wind and magnetospheric particles
  being funneled down and accelerated along the Earth's magnetic field
  lines; excitation energy is lost by the emission of a photon, or by
  collision with another atom or molecule:</p>
  
  <ul>
  <li><p><strong>oxygen emissions</strong>: green or brownish-red, depending on the amount of energy absorbed.</p></li>
  <li><p><strong>nitrogen emissions</strong>: blue or red; blue if the atom regains an electron after it has been ionized, red if returning to ground state from an excited state.</p></li>
  </ul>
  
  <p>Oxygen is unusual in terms of its return to ground state: it can take
  three quarters of a second to emit green light and up to two minutes
  to emit red. Collisions with other atoms or molecules absorb the
  excitation energy and prevent emission. Because the very top of the
  atmosphere has a higher percentage of oxygen and is sparsely
  distributed such collisions are rare enough to allow time for oxygen
  to emit red. Collisions become more frequent progressing down into the
  atmosphere, so that red emissions do not have time to happen, and
  eventually even green light emissions are prevented.</p>
  
  <p>This is why there is a color differential with altitude; at high
  altitude oxygen red dominates, then oxygen green and nitrogen
  blue/red, then finally nitrogen blue/red when collisions prevent
  oxygen from emitting anything. Green is the most common of all
  auroras. Behind it is pink, a mixture of light green and red, followed
  by pure red, yellow (a mixture of red and green), and finally, pure
  blue.</p>
</blockquote>

CC BY-SA 3.0
2014-04-16T11:10:47.463Z
Thanks naught, but as I said I am not going to choose an answer that is just copied from wikipedia.  I would rather this be a site that people come to instead of wikipedia for better synthesized answers, than merely another copycat site.
Kenshin
CC BY-SA 3.0
2014-04-16T11:11:46.890Z
Fair enough, but I doubt there are many other references that put it as succinctly, and if it's already written, why bother re-writing it?
naught101
CC BY-SA 3.0
2014-04-16T11:09:22.113Z
2014-04-16T11:09:22.113Z
naught101
<p>What is the scientific reason for the majestic sights of the northern and southern lights, otherwise known as Auroras near the magnetic poles, and why do the northern lights differ from the southern lights?</p>

<p><img src="https://i.sstatic.net/9mVih.jpg" alt="enter image description here"></p>

CC BY-SA 3.0
2014-04-16T08:45:53.920Z
I'm not able to find any sources for the difference between the auroras except the location, do you have some? Resources [Aurora Borealis or Northern Lights](http://geography.about.com/od/physicalgeography/a/Aurora-Borealis-Or-Northern-Lights.htm) and [Aurora on wikipedia](http://en.wikipedia.org/wiki/Aurora)
bummi
CC BY-SA 3.0
2014-04-16T08:54:04.500Z
*Do* they differ? I'm curious now.... :-)
Semidiurnal Simon
CC BY-SA 3.0
2014-04-16T10:49:16.067Z
The wikipedia page goes into a lot of depth about why and how auroras happen, and also the causes of some of the differences (e.g. colours). There probably isn't much point in answering this question as it stands, as it would just be a copy and paste from wikipedia. Is there a way you feel like you could modify your question to make it more useful to the site?
naught101
CC BY-SA 3.0
2014-04-16T10:55:11.177Z
@naught101, I didn't realize that we can't ask questions that already have an answer elsewhere on the internet. That's a great plan for an answer rate below the 90% required to get this site out of beta. Perhaps a good answer will nicely summarize what is written on the wikipedia article.
Kenshin
CC BY-SA 3.0
2014-04-16T11:03:11.820Z
@mew, see http://blog.stackoverflow.com/2011/02/are-some-questions-too-simple/. I'm not sure about this, but I kinda feel like early on, we should be focussing on questions that bring people to the site (because the answer is here), rather than take them away (because the answer is just a link to elsewhere, or has more interesting, easy to read detail at the link).
naught101
CC BY-SA 3.0
2014-04-16T11:04:49.437Z
@naught101, we shouldn't just link to wikipedia. I'm sure wikipedia isn't the only source, and I'm sure it isn't the best source on this topic.  Instead one should look at a variety of sources such as the internet, and textbooks to compose an answer to my question.  I'm not going to accept an answer that just links to wikipedia and we should not upvote those answers.
Kenshin
CC BY-SA 3.0
2014-04-16T11:36:30.990Z
IMHO the problem is with *questions* that can be fully and completely answered with a copy/paste from Wikipedia. See my meta question here: http://meta.earthscience.stackexchange.com/questions/34/level-of-the-questions-so-far If we ask and answer questions in private beta that are not of interest to experts, we will set the tone of the site at a "popular science" level and not get the experts that we want to stay with the site and grow it.
Semidiurnal Simon
CC BY-SA 3.0
2014-04-16T11:45:10.447Z
@SimonW, private beta has a maximum of about 200 experts.  I understand your problem, but try and understand mine.  I have committed to many proposals and very few have ever made it past this private beta stage because of these ideals and because noone answers the questions.  If we ask hard questions, we won't get much answers, and our site will be taken down within the week because of a lack of answers being provided.
Kenshin
CC BY-SA 3.0
2014-04-16T12:08:51.063Z
@Mew Hmm, interesting. This is my first private beta, but... that wasn't the understanding that I got from the blurb that was issued, which was all about "setting the tone" of what the site would become. But, I understand your point :-)
Semidiurnal Simon
CC BY-SA 3.0
2014-04-16T12:11:07.280Z
@SimonW, the last private beta I was in last week shut down after 4 days, despite lots of questions, but not enough answers.  It's a tough process.
Kenshin
<auroras>
What causes the beautiful Auroras on the north and south magnetic poles?
Kenshin
# What causes the beautiful Auroras on the north and south magnetic poles?

(Asked by: username_0 on 2014-04-16)

What is the scientific reason for the majestic sights of the northern and southern lights, otherwise known as Auroras near the magnetic poles, and why do the northern lights differ from the southern lights?

![enter image description here](https://i.sstatic.net/9mVih.jpg)

**Tags:** auroras

> **Comments:**
> **username_1**: I'm not able to find any sources for the difference between the auroras except the location, do you have some? Resources [Aurora Borealis or Northern Lights](http://geography.about.com/od/physicalgeography/a/Aurora-Borealis-Or-Northern-Lights.htm) and [Aurora on wikipedia](http://en.wikipedia.org/wiki/Aurora)  
> **username_2**: *Do* they differ? I'm curious now.... :-)  
> **username_3**: The wikipedia page goes into a lot of depth about why and how auroras happen, and also the causes of some of the differences (e.g. colours). There probably isn't much point in answering this question as it stands, as it would just be a copy and paste from wikipedia. Is there a way you feel like you could modify your question to make it more useful to the site?  
> **username_0**: @username_3, I didn't realize that we can't ask questions that already have an answer elsewhere on the internet. That's a great plan for an answer rate below the 90% required to get this site out of beta. Perhaps a good answer will nicely summarize what is written on the wikipedia article.  
> **username_3**: @mew, see http://blog.stackoverflow.com/2011/02/are-some-questions-too-simple/. I'm not sure about this, but I kinda feel like early on, we should be focussing on questions that bring people to the site (because the answer is here), rather than take them away (because the answer is just a link to elsewhere, or has more interesting, easy to read detail at the link).  
> **username_0**: @username_3, we shouldn't just link to wikipedia. I'm sure wikipedia isn't the only source, and I'm sure it isn't the best source on this topic.  Instead one should look at a variety of sources such as the internet, and textbooks to compose an answer to my question.  I'm not going to accept an answer that just links to wikipedia and we should not upvote those answers.  
> **username_2**: IMHO the problem is with *questions* that can be fully and completely answered with a copy/paste from Wikipedia. See my meta question here: http://meta.earthscience.stackexchange.com/questions/34/level-of-the-questions-so-far If we ask and answer questions in private beta that are not of interest to experts, we will set the tone of the site at a "popular science" level and not get the experts that we want to stay with the site and grow it.  
> **username_0**: @SimonW, private beta has a maximum of about 200 experts.  I understand your problem, but try and understand mine.  I have committed to many proposals and very few have ever made it past this private beta stage because of these ideals and because noone answers the questions.  If we ask hard questions, we won't get much answers, and our site will be taken down within the week because of a lack of answers being provided.  
> **username_2**: @Mew Hmm, interesting. This is my first private beta, but... that wasn't the understanding that I got from the blurb that was issued, which was all about "setting the tone" of what the site would become. But, I understand your point :-)  
> **username_0**: @SimonW, the last private beta I was in last week shut down after 4 days, despite lots of questions, but not enough answers.  It's a tough process.  

---

## 2 answers

### Answer by username_4 on 2014-04-16. Score: 0 | Accepted answer

The Auroras are formed because a reconnection in the magnetic field. Particles are emitted by the Sun and collide with our magnetic field. This collision generates effects in the ionosphere. You can read more about it in these links:

<http://www.atoptics.co.uk/highsky/auror2.htm>

<http://mrx.pppl.gov/Physics/physics.html>

> **Comments:**
> **username_2**: Hi dlOGO. It's discouraged to just give links in Stackexchange answers. Could you consider summarising the content of the links? Thanks.  
> **username_5**: This answer is incorrect.  The reason is not that they collide with the magnetic field (in fact, they don't, but are merely deflected by it), but they collide with the upper atmosphere.  The answer also doesn't explain how that causes visible aurorae.  

---

### Answer by username_3 on 2014-04-16. Score: 3

Straight from [wikipedia](https://en.wikipedia.org/wiki/Aurora#Auroral_mechanism):

> Auroras are associated with the solar wind, a flow of ions
> continuously flowing outward from the Sun. The Earth's magnetic field
> traps these particles, many of which travel toward the poles where
> they are accelerated toward Earth. Collisions between these ions and
> atmospheric atoms and molecules cause energy releases in the form of
> auroras appearing in large circles around the poles. Auroras are more
> frequent and brighter during the intense phase of the solar cycle when
> coronal mass ejections increase the intensity of the solar wind.
>
> Auroras result from emissions of photons in the Earth's upper
> atmosphere, above 80 km (50 mi), from ionized nitrogen molecules
> regaining an electron, and oxygen atoms and nitrogen molecules
> returning from an excited state to ground state. They are ionized
> or excited by the collision of solar wind and magnetospheric particles
> being funneled down and accelerated along the Earth's magnetic field
> lines; excitation energy is lost by the emission of a photon, or by
> collision with another atom or molecule:
>
> * **oxygen emissions**: green or brownish-red, depending on the amount of energy absorbed.
> * **nitrogen emissions**: blue or red; blue if the atom regains an electron after it has been ionized, red if returning to ground state from an excited state.
>
> Oxygen is unusual in terms of its return to ground state: it can take
> three quarters of a second to emit green light and up to two minutes
> to emit red. Collisions with other atoms or molecules absorb the
> excitation energy and prevent emission. Because the very top of the
> atmosphere has a higher percentage of oxygen and is sparsely
> distributed such collisions are rare enough to allow time for oxygen
> to emit red. Collisions become more frequent progressing down into the
> atmosphere, so that red emissions do not have time to happen, and
> eventually even green light emissions are prevented.
>
> This is why there is a color differential with altitude; at high
> altitude oxygen red dominates, then oxygen green and nitrogen
> blue/red, then finally nitrogen blue/red when collisions prevent
> oxygen from emitting anything. Green is the most common of all
> auroras. Behind it is pink, a mixture of light green and red, followed
> by pure red, yellow (a mixture of red and green), and finally, pure
> blue.

> **Comments:**
> **username_0**: Thanks naught, but as I said I am not going to choose an answer that is just copied from wikipedia.  I would rather this be a site that people come to instead of wikipedia for better synthesized answers, than merely another copycat site.  
> **username_3**: Fair enough, but I doubt there are many other references that put it as succinctly, and if it's already written, why bother re-writing it?  

---

