<p>Auroras start at a distance of 80-200 km above the Earth's surface.</p>

<p>The color of the aurora will be blue/purple if the air molecules in the area below 120 km are excited.</p>

<p>If the air molecules in the area from 120-180 km are the ones that gets excited the colour will be yellow/green.</p>

<p>Above 180 km gives the red light in the aurora.</p>

<p>The most powerful aurora will in general be 180 degree from the Sun's position and it will move from east to west at the opposite side to where the Sun is.</p>

<p>During powerful auroras the aurora arch can easily cover 270 degrees or more if close to the magnetic poles, if the aurora covers the area away from the magnetic poles the aurora arch will get smaller.</p>

<p>When the charged particles from the Sun interact with Earth's magnetic field a powerful ground current will be induced, this can induce DC power in power lines and severely damage the AC power transformers. Should an event like the one that happened on September the first, 1859 (the Carrington event) hit us today we would have major problems with power supply and satellite communication.</p>

<p>You can read more about all of this here, <a href="https://en.wikipedia.org/wiki/Aurora" rel="noreferrer">Aurora</a> and please take a look in the sources there too.</p>

CC BY-SA 4.0
2020-01-26T06:29:37.430Z
2020-01-26T11:09:19.873Z
2020-01-26T11:09:19.873Z
trond hansen
<p>Aurora Australis and Aurora Borealis occur as a result of the upper atmosphere being bombarded with sub atomic particles (protons and electrons) from the solar wind. Solar winds are mass ejections from magnetic storms on the sun, and vary in intensity and frequency. These particles are electrically charged and deflected toward the poles by the Earth's magnetic field. </p>

<p>The aurorae have a tendency to be displaced toward the night time side of the Earth and to move very slowly from west to east because the magnetic poles are slightly off-centre and rotate with the rotation of the Earth. Films on TV often show the aurora speeded up, but usually their movement is only barely perceptible to the naked eye. If you can see the background stars moving, the movie has been speeded up. The ones I saw with the naked eye moved very slowly.</p>

<p>There are two main colours. Green is by far the most common, but occasionally the aurora is red. I have seen both from southern England. The red ones are caused by solar wind particles striking and exciting oxygen atoms in the high, upper atmosphere, causing them to emit a reddish light. These particles also vary in velocity, so the more powerful ones are able to reach further down into the atmosphere and stimulate a much stronger emission of green light from nitrogen atoms. This overwhelms the fainter red light from oxygen, so the aurora looks green. They are not often seen from southern England. It sometimes happens, but only in the winter with a very clear sky.</p>

CC BY-SA 4.0
2020-01-25T11:47:18.190Z
I know what the colours are, because I've seen them. Your chances of seeing infra-red or ultraviolet are exactly nil.
Michael Walsby
CC BY-SA 4.0
2020-01-25T17:02:45.130Z
I wasn't asking how the aurorae formed, what color they are, or how quickly they move.  I'm wanting to know if I was standing at McMurdo Station, on Ross Island in Antarctica, facing east would would I likely see an aurora coming from the east moving to the west, or from the west to the east, or is it completely unpredictable?
Bob516
CC BY-SA 4.0
2020-01-25T19:20:12.647Z
ebv says you want to know how they move, you say you don't. Who am I supposed to believe? Aurorae are often present by day,because the charged particles take hours to reach us from the sun,and different outbursts move at different speeds, so unlike photons their time of arrival is not easily predictable unless you know their speed. Photons always move at 186,000 miles per sec, much faster than protons and electrons,and it never varies. In all important respects, Aurora Australis is the same as A. Borealis. The Earth is not always the same distance from the sun, which adds another complication.
Michael Walsby
CC BY-SA 4.0
2020-01-25T22:00:13.510Z
@MichaelWalsby In my question I asked, "Do they tend to begin and MOVE from east to west, or west to east or is it entirely random?" in my comment I asked, "would I likely see an aurora coming from the east MOVING to the west," (emphasis added).  I don't understand the confusion.
Bob516
CC BY-SA 4.0
2020-01-25T22:31:13.597Z
West to east, because that is the way the off-centre magnetic poles move with the rotation of the Earth. Being electrically charged, the particles are deflected to the poles by the Earth's magnetic field. At maximum eccentricity they have 12 percent further to travel than at minimum eccentricity. This would delay a photon only slightly because they travel so fast, but charged particles travel very much slower. A hell of a lot slower. They originate in magnetic storms on the sun.
Michael Walsby
CC BY-SA 4.0
2020-01-27T10:00:56.123Z
"The aurorae have a tendency to be displaced toward the night time side of the Earth and to move very slowly from west to east because the magnetic poles are slightly off-centre and rotate with the rotation of the Earth" Surely if that were the main mechanism them the aurorae would always be strongest over the same part of the earth, dictated by the position of the magnetic poles?
Semidiurnal Simon
CC BY-SA 4.0
2020-01-27T10:05:58.337Z
I think the position, colour and strength of the aurorae are influenced by the qualities of the solar wind which creates them. As you know, this wind is very variable.
Michael Walsby
CC BY-SA 4.0
2020-01-28T12:35:55.510Z
@MichaelWalsby no, you don't get to do this. You specifically asserted that the aurora tend to move west to east because of the offset of magnetic poles. I queried that specific point, and you responded by vaguely going "eh, it's very variable". Do you know that you were right, or were you just guessing? If you were just guessing, you owe it to users of this site to remove that info from your answer.
Semidiurnal Simon
CC BY-SA 4.0
2020-01-25T10:04:47.303Z
2020-01-25T10:25:41.097Z
2020-01-25T10:25:41.097Z
Michael Walsby
<p>During a polar night is there any pattern or consistency to where aurorae australis begin?  I'm assuming they become visible first in the exosphere and descend down to thermosphere.  Do they tend to begin and move from east to west, or west to east or is it entirely random?</p>

CC BY-SA 4.0
2020-01-25T06:06:35.803Z
please take a look here https://en.wikipedia.org/wiki/Aurora and edit your question so it only is one question,it will be a lot easier to answer your question if we know what level of knowledge you have.
trond hansen
CC BY-SA 4.0
2020-01-25T16:40:45.650Z
for anybody interrested in auroras and spaceweather here is a couple of links https://spaceweather.com/ and a live aurora map https://earth.nullschool.net/#current/space/surface/level/anim=off/overlay=aurora/orthographic=-47.36,89.91,1161
trond hansen
<auroras>
Where do aurorae australis begin and in which direction do they move?
Bob516
# Where do aurorae australis begin and in which direction do they move?

(Asked by: username_0 on 2020-01-25)

During a polar night is there any pattern or consistency to where aurorae australis begin? I'm assuming they become visible first in the exosphere and descend down to thermosphere. Do they tend to begin and move from east to west, or west to east or is it entirely random?

**Tags:** auroras

> **Comments:**
> **username_1**: please take a look here https://en.wikipedia.org/wiki/Aurora and edit your question so it only is one question,it will be a lot easier to answer your question if we know what level of knowledge you have.  
> **username_1**: for anybody interrested in auroras and spaceweather here is a couple of links https://spaceweather.com/ and a live aurora map https://earth.nullschool.net/#current/space/surface/level/anim=off/overlay=aurora/orthographic=-47.36,89.91,1161  

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## 2 answers

### Answer by username_1 on 2020-01-26. Score: 7

Auroras start at a distance of 80-200 km above the Earth's surface.

The color of the aurora will be blue/purple if the air molecules in the area below 120 km are excited.

If the air molecules in the area from 120-180 km are the ones that gets excited the colour will be yellow/green.

Above 180 km gives the red light in the aurora.

The most powerful aurora will in general be 180 degree from the Sun's position and it will move from east to west at the opposite side to where the Sun is.

During powerful auroras the aurora arch can easily cover 270 degrees or more if close to the magnetic poles, if the aurora covers the area away from the magnetic poles the aurora arch will get smaller.

When the charged particles from the Sun interact with Earth's magnetic field a powerful ground current will be induced, this can induce DC power in power lines and severely damage the AC power transformers. Should an event like the one that happened on September the first, 1859 (the Carrington event) hit us today we would have major problems with power supply and satellite communication.

You can read more about all of this here, [Aurora](https://en.wikipedia.org/wiki/Aurora) and please take a look in the sources there too.


---

### Answer by username_2 on 2020-01-25. Score: -8

Aurora Australis and Aurora Borealis occur as a result of the upper atmosphere being bombarded with sub atomic particles (protons and electrons) from the solar wind. Solar winds are mass ejections from magnetic storms on the sun, and vary in intensity and frequency. These particles are electrically charged and deflected toward the poles by the Earth's magnetic field.

The aurorae have a tendency to be displaced toward the night time side of the Earth and to move very slowly from west to east because the magnetic poles are slightly off-centre and rotate with the rotation of the Earth. Films on TV often show the aurora speeded up, but usually their movement is only barely perceptible to the naked eye. If you can see the background stars moving, the movie has been speeded up. The ones I saw with the naked eye moved very slowly.

There are two main colours. Green is by far the most common, but occasionally the aurora is red. I have seen both from southern England. The red ones are caused by solar wind particles striking and exciting oxygen atoms in the high, upper atmosphere, causing them to emit a reddish light. These particles also vary in velocity, so the more powerful ones are able to reach further down into the atmosphere and stimulate a much stronger emission of green light from nitrogen atoms. This overwhelms the fainter red light from oxygen, so the aurora looks green. They are not often seen from southern England. It sometimes happens, but only in the winter with a very clear sky.

> **Comments:**
> **username_2**: I know what the colours are, because I've seen them. Your chances of seeing infra-red or ultraviolet are exactly nil.  
> **username_0**: I wasn't asking how the aurorae formed, what color they are, or how quickly they move.  I'm wanting to know if I was standing at McMurdo Station, on Ross Island in Antarctica, facing east would would I likely see an aurora coming from the east moving to the west, or from the west to the east, or is it completely unpredictable?  
> **username_2**: ebv says you want to know how they move, you say you don't. Who am I supposed to believe? Aurorae are often present by day,because the charged particles take hours to reach us from the sun,and different outbursts move at different speeds, so unlike photons their time of arrival is not easily predictable unless you know their speed. Photons always move at 186,000 miles per sec, much faster than protons and electrons,and it never varies. In all important respects, Aurora Australis is the same as A. Borealis. The Earth is not always the same distance from the sun, which adds another complication.  
> **username_0**: @username_2 In my question I asked, "Do they tend to begin and MOVE from east to west, or west to east or is it entirely random?" in my comment I asked, "would I likely see an aurora coming from the east MOVING to the west," (emphasis added).  I don't understand the confusion.  
> **username_2**: West to east, because that is the way the off-centre magnetic poles move with the rotation of the Earth. Being electrically charged, the particles are deflected to the poles by the Earth's magnetic field. At maximum eccentricity they have 12 percent further to travel than at minimum eccentricity. This would delay a photon only slightly because they travel so fast, but charged particles travel very much slower. A hell of a lot slower. They originate in magnetic storms on the sun.  
> **username_3**: "The aurorae have a tendency to be displaced toward the night time side of the Earth and to move very slowly from west to east because the magnetic poles are slightly off-centre and rotate with the rotation of the Earth" Surely if that were the main mechanism them the aurorae would always be strongest over the same part of the earth, dictated by the position of the magnetic poles?  
> **username_2**: I think the position, colour and strength of the aurorae are influenced by the qualities of the solar wind which creates them. As you know, this wind is very variable.  
> **username_3**: @username_2 no, you don't get to do this. You specifically asserted that the aurora tend to move west to east because of the offset of magnetic poles. I queried that specific point, and you responded by vaguely going "eh, it's very variable". Do you know that you were right, or were you just guessing? If you were just guessing, you owe it to users of this site to remove that info from your answer.  

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