<p>The reason is because of Earth's global magnetic field. Take a look at the image below which shows a representation of what the magnetic field lines around Earth look like.</p>

<p><a href="https://i.sstatic.net/lQNc2.jpg" rel="noreferrer"><img src="https://i.sstatic.net/lQNc2.jpg" alt="Earth&#39;s magnetic field"></a></p>

<p>What you see above is what's known as a <a href="https://en.wikipedia.org/wiki/Magnetic_dipole" rel="noreferrer">Magnetic Dipole</a> field. The reason being that there are two (Di means two) magnetic poles, namely the north pole and the south pole. This is completely analogous to a giant bar magnet you may have played with in science class. You can see here that the field lines leave the magnetic south pole and travel around, going up into the magnetic north pole. The field lines don't really leave from or enter the Earth's equator.</p>

<p>But why does this mean aurora's happen at the poles? Because, according to the theory of electromagnetism, charged particles are forced to travel only along magnetic field lines. They cannot travel across them or break free from them. Once they get stuck, they're stuck (this isn't 100% true but for the purposes of this answer, it is). Note that the particles can travel both forward and backward on the field lines. They're not constrained to going only in the direction of the field line. This means that the primary location in which these charged particles can enter the Earth's atmosphere is where the field lines tend to hit the atmosphere and we already noted that that location was the magnetic north and south pole (which coincidentally is near the physical north and south pole).</p>

<p>Auroras themselves are just emissions from our atmosphere in response to being bombarded by high energy particles. To put this all together, here's what happens: The Sun spews out huge amounts of energy and tons of charged particles. Some of those charged particles hit the Earth's magnetic field and get trapped in it, being forced to travel along the magnetic field lines. They are then constrained to primarily hit the Earth's atmosphere at the magnetic poles where their extreme energy excites the atmosphere, causing it to emit light in shimmering red and green sheets. The auroras can't occur at the equator simply because not enough particles can hit the atmosphere there to cause auroras.</p>

<p>One day though, we may see auroras at the equator. The Earth's magnetic field is not fixed and moves with time. About every 450,000 years the field flips around completely. Its been about <a href="http://www.astronoo.com/en/articles/magnetosphere-earth.html" rel="noreferrer">750,000 years</a> since the last reversal so we're due for one potentially soon (and by soon I mean in the next few thousand or tens of thousands of years). During the flip, while the magnetic poles are over the equator, you'll see auroras there.</p>

CC BY-SA 3.0
2017-03-07T19:03:01.443Z
This is misleading.  See "magnetic midnight" for example, or auroras due to CME.
Carl Witthoft
CC BY-SA 3.0
2017-03-07T19:05:18.720Z
@CarlWitthoft I realize I state some half-truths, but given the knowledge level of the questioner, I didn't want to overly complicate things with caveats and exceptions. Even that picture above isn't really a good "model" of the Earth's magnetic field.
zephyr
CC BY-SA 3.0
2017-03-07T13:57:35.617Z
2017-03-07T14:30:07.123Z
2017-03-07T14:30:07.123Z
zephyr
<p>I realize this is an older question, but wanted to provide some clarification on the great answer that zephyr gave, and that is, the magnetic field does not instantaneously shift: it is not like a switch (thankfully, because that could be catastrophic). What it does is shift over time by slowly weakening, then becoming rather complex, before reforming in the opposite direction. This happens because of the motions within the Earth's molten core, which are chaotic. See, for example, <a href="https://www.usgs.gov/faqs/it-true-earths-magnetic-field-occasionally-reverses-its-polarity" rel="nofollow noreferrer">this U.S. Geological Survey post</a>.</p>
<p>This leads me to my second clarification. Just like earthquakes and volcanoes, there is not such a thing as &quot;due&quot;. There are statistical averages in how often they have occurred in the past, but those are not metrics that can be used to predict the next occurrence.</p>
<p>The movements of the inner core are completely chaotic. The shift may begin next year, it might already have begun, or it might not begin for another 500,000 years. The time between two events is fed into the formula to adjust the current average, but the average does not predict the next event. Looking at how long it has been since the last one and what the current average is, is a really good example of this. People get the wrong idea when we say &quot;We are due to have an event&quot;: it will probably happen at some point, but we are not &quot;due&quot;.</p>

CC BY-SA 4.0
2024-11-07T03:50:34.007Z
Welcome to Astronomy SE! Do you have any sources to support your answer?
WarpPrime
CC BY-SA 4.0
2024-11-07T05:26:14.007Z
Hi El Sergio, welcome to Astronomy.SE! While your post is technically a comment on @zephyr's answer, we do allow (and encourage) answers that clarify or elaborate on an existing answer and are too long to be posted as a comment. However, we still expect such answers to be *authoritative*. The easiest way to achieve this is to [edit](https://astronomy.stackexchange.com/posts/58873/edit) your post to add a reference supporting your statement that the magnetic poles don't "flip" but take time to change. I'd be happy to upvote your answer if you added a reference. :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2024-11-07T05:55:05.643Z
LOL... I've edited your answer myself. The "frequency" issue intrigued me, so I did a quick search for how often the magnetic field have changed, & ended up finding a suitable reference for your post! And yes, how frustrating the people in the sciences don't understand how statistical probability works. BTW, don't forget to earn yourself a badge by taking our *[Tour]*. :-)
Chappo Hasn't Forgotten
CC BY-SA 4.0
2024-11-08T05:26:56.613Z
Thank you @ChappoHasn'tForgotten, it would not let me post a comment, which I initially tried. Citing sources makes sense, and I'll be sure to do so moving forward.  I'll take the tour and fill out profile now, thanks for the welcome and assist!
El Sergio
CC BY-SA 4.0
2024-11-07T01:44:43.977Z
2024-11-07T05:47:42.220Z
2024-11-07T05:47:42.220Z
El Sergio
<p>Why is it that Auroras only occur in the North and South poles. Why don't they occur in the equator or anywhere for that matter?</p>

CC BY-SA 3.0
2017-03-07T14:05:45.453Z
This is incorrect.  The probability of occurrence is higher there but auroras can be seen well below the Arctic zones.
Carl Witthoft
CC BY-SA 3.0
2017-03-07T21:08:32.540Z
Why the downvote? This is a perfectly valid question even if it exhibits some misunderstandings about auroras.
zephyr
<aurora>
Why do Auroras only occur in polar regions?
Mihir Shah
# Why do Auroras only occur in polar regions?

(Asked by: username_0 on 2017-03-07)

Why is it that Auroras only occur in the North and South poles. Why don't they occur in the equator or anywhere for that matter?

**Tags:** aurora

> **Comments:**
> **username_1**: This is incorrect.  The probability of occurrence is higher there but auroras can be seen well below the Arctic zones.  
> **username_2**: Why the downvote? This is a perfectly valid question even if it exhibits some misunderstandings about auroras.  

---

## 2 answers

### Answer by username_2 on 2017-03-07. Score: 8

The reason is because of Earth's global magnetic field. Take a look at the image below which shows a representation of what the magnetic field lines around Earth look like.

[![Earth's magnetic field](https://i.sstatic.net/lQNc2.jpg)](https://i.sstatic.net/lQNc2.jpg)

What you see above is what's known as a [Magnetic Dipole](https://en.wikipedia.org/wiki/Magnetic_dipole) field. The reason being that there are two (Di means two) magnetic poles, namely the north pole and the south pole. This is completely analogous to a giant bar magnet you may have played with in science class. You can see here that the field lines leave the magnetic south pole and travel around, going up into the magnetic north pole. The field lines don't really leave from or enter the Earth's equator.

But why does this mean aurora's happen at the poles? Because, according to the theory of electromagnetism, charged particles are forced to travel only along magnetic field lines. They cannot travel across them or break free from them. Once they get stuck, they're stuck (this isn't 100% true but for the purposes of this answer, it is). Note that the particles can travel both forward and backward on the field lines. They're not constrained to going only in the direction of the field line. This means that the primary location in which these charged particles can enter the Earth's atmosphere is where the field lines tend to hit the atmosphere and we already noted that that location was the magnetic north and south pole (which coincidentally is near the physical north and south pole).

Auroras themselves are just emissions from our atmosphere in response to being bombarded by high energy particles. To put this all together, here's what happens: The Sun spews out huge amounts of energy and tons of charged particles. Some of those charged particles hit the Earth's magnetic field and get trapped in it, being forced to travel along the magnetic field lines. They are then constrained to primarily hit the Earth's atmosphere at the magnetic poles where their extreme energy excites the atmosphere, causing it to emit light in shimmering red and green sheets. The auroras can't occur at the equator simply because not enough particles can hit the atmosphere there to cause auroras.

One day though, we may see auroras at the equator. The Earth's magnetic field is not fixed and moves with time. About every 450,000 years the field flips around completely. Its been about [750,000 years](http://www.astronoo.com/en/articles/magnetosphere-earth.html) since the last reversal so we're due for one potentially soon (and by soon I mean in the next few thousand or tens of thousands of years). During the flip, while the magnetic poles are over the equator, you'll see auroras there.

> **Comments:**
> **username_1**: This is misleading.  See "magnetic midnight" for example, or auroras due to CME.  
> **username_2**: @username_1 I realize I state some half-truths, but given the knowledge level of the questioner, I didn't want to overly complicate things with caveats and exceptions. Even that picture above isn't really a good "model" of the Earth's magnetic field.  

---

### Answer by username_3 on 2024-11-07. Score: 4

I realize this is an older question, but wanted to provide some clarification on the great answer that username_2 gave, and that is, the magnetic field does not instantaneously shift: it is not like a switch (thankfully, because that could be catastrophic). What it does is shift over time by slowly weakening, then becoming rather complex, before reforming in the opposite direction. This happens because of the motions within the Earth's molten core, which are chaotic. See, for example, [this U.S. Geological Survey post](https://www.usgs.gov/faqs/it-true-earths-magnetic-field-occasionally-reverses-its-polarity).

This leads me to my second clarification. Just like earthquakes and volcanoes, there is not such a thing as "due". There are statistical averages in how often they have occurred in the past, but those are not metrics that can be used to predict the next occurrence.

The movements of the inner core are completely chaotic. The shift may begin next year, it might already have begun, or it might not begin for another 500,000 years. The time between two events is fed into the formula to adjust the current average, but the average does not predict the next event. Looking at how long it has been since the last one and what the current average is, is a really good example of this. People get the wrong idea when we say "We are due to have an event": it will probably happen at some point, but we are not "due".

> **Comments:**
> **username_4**: Welcome to Astronomy SE! Do you have any sources to support your answer?  
> **username_5**: Hi El username_3, welcome to Astronomy.SE! While your post is technically a comment on @username_2's answer, we do allow (and encourage) answers that clarify or elaborate on an existing answer and are too long to be posted as a comment. However, we still expect such answers to be *authoritative*. The easiest way to achieve this is to [edit](https://astronomy.stackexchange.com/posts/58873/edit) your post to add a reference supporting your statement that the magnetic poles don't "flip" but take time to change. I'd be happy to upvote your answer if you added a reference. :-)  
> **username_5**: LOL... I've edited your answer myself. The "frequency" issue intrigued me, so I did a quick search for how often the magnetic field have changed, & ended up finding a suitable reference for your post! And yes, how frustrating the people in the sciences don't understand how statistical probability works. BTW, don't forget to earn yourself a badge by taking our *[Tour]*. :-)  
> **username_3**: Thank you @username_5, it would not let me post a comment, which I initially tried. Citing sources makes sense, and I'll be sure to do so moving forward.  I'll take the tour and fill out profile now, thanks for the welcome and assist!  

---

