<p>In fact multiple species of oxygen or nitrogen can create emissions at various wavelengths. There can be aurorae over a wide range of wavelengths, we just see only some of them that happen to be in the visible range. So, it's all a matter of which species hit the relatively narrow visible target.</p>
<p>With respect to oxygen, Rezaei et al. <a href="https://i.sstatic.net/3qmbT.png" rel="nofollow noreferrer">1</a> provide this spectrum, in which atomic oxygen produces an emission near the red end of the visible range, while ions of both monatomic and diatomic oxygen give less intense emissions of various colors from blue to orange. Note that no emission is listed for neutral <span class="math-container">$\text{O}_2$</span>.</p>
<p><a href="https://i.sstatic.net/3qmbT.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/3qmbT.png" alt="enter image description here" /></a></p>
<p>With nitrogen, similar results from Hosseini et al. <a href="https://i.sstatic.net/SPos8.png" rel="nofollow noreferrer">2</a> show an emission in the violet or blue range from ionized diatomic nitrogen, but none from any monatomuc nitrogen species. Note that in this spectrum the red eemission from atomic oxygen is seen, apparently from a small amount of this imputity in the gas sample.</p>
<p><a href="https://i.sstatic.net/SPos8.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/SPos8.png" alt="enter image description here" /></a></p>
<p><strong>References</strong></p>
<p>1.
Rezaei, Fatemeh &amp; Abbasi-Firouzjah, Marzieh &amp; Shokri, Babak (2014). &quot;Investigation of antibacterial and wettability behaviours of plasma-modified PMMA films for application in ophthalmology&quot;, <em>Journal of Physics D Applied Physics</em>, <strong>47</strong>, 085401. <a href="https://doi.org/10.1088/0022-3727/47/8/085401" rel="nofollow noreferrer">https://doi.org/10.1088/0022-3727/47/8/085401</a>.</p>
<p>2.
Hosseini, Seyed Iman &amp; Mohsenimehr, Soad &amp; Hadian, Javad &amp; Ghorbanpour, Mansour &amp; Shokri, Babak (2018). &quot;Physico-chemical induced modification of seed germination and early development in artichoke ( Cynara scolymus L.) using low energy plasma technology&quot;, <em>Physics of Plasmas</em>, <strong>25</strong>, 013525. <a href="https://doi.org/10.1063/1.5016037" rel="nofollow noreferrer">https://doi.org/10.1063/1.5016037</a>.</p>

CC BY-SA 4.0
2022-03-01T02:18:04.323Z
How are your two answers different? Why not just edit the first answer if you wanted to add, remove or clarify something?
Fred
CC BY-SA 4.0
2022-03-01T02:26:31.810Z
Sorry, it was an accident. Will delete the other one.
Oscar Lanzi
CC BY-SA 4.0
2022-02-27T23:02:09.543Z
2022-03-07T11:25:25.800Z
2022-03-07T11:25:25.800Z
Oscar Lanzi
<p>Firstly, since there are a lot of oxygen atoms at a height of 200km, and less energy is needed to produce a red aurora than a green aurora, so it should be easier to produce red auroras than green auroras and we should see more red auroras than green auroras, but we see more green aurora in reality. Why are red auroras rare? Is it true that red auroras need 200s for the 630 nm transition?</p>
<p>Secondly, why do oxygen atoms (not oxygen molecules) cause auroras while molecular nitrogen cause auroras instead of atomic nitrogen?</p>

CC BY-SA 4.0
2021-09-22T17:04:03.953Z
The first aurora I saw in the southern hemisphere was a red aurora. However, I haven't seen many auroras down here.
Fred
CC BY-SA 4.0
2021-09-23T13:23:15.723Z
Don't forget that human eyes are more sensitive to green than to red, and in low-light conditions even more to cyan than to green. So red auroras might be frequent but not bright enough to see.
Ruslan
CC BY-SA 4.0
2021-09-28T02:52:51.090Z
To Fred, where are you located?
Lisa Baron
CC BY-SA 4.0
2021-09-28T02:53:25.097Z
To Ruslan, Why are we more sensitive to green light when 65% of our cone cells are red cone cells?
Lisa Baron
CC BY-SA 4.0
2021-10-05T16:24:48.667Z
Atoms or molecules of anything up there cause auroras. The question is, which sources give results that land in our visible frequency range?
Oscar Lanzi
<atmosphere><upper-atmosphere><auroras>
Why are red auroras rare? Why do oxygen atoms (not oxygen molecules) cause auroras while molecular nitrogen cause auroras instead of atomic nitrogen?
Lisa Baron
# Why are red auroras rare? Why do oxygen atoms (not oxygen molecules) cause auroras while molecular nitrogen cause auroras instead of atomic nitrogen?

(Asked by: username_0 on 2021-09-22)

Firstly, since there are a lot of oxygen atoms at a height of 200km, and less energy is needed to produce a red aurora than a green aurora, so it should be easier to produce red auroras than green auroras and we should see more red auroras than green auroras, but we see more green aurora in reality. Why are red auroras rare? Is it true that red auroras need 200s for the 630 nm transition?

Secondly, why do oxygen atoms (not oxygen molecules) cause auroras while molecular nitrogen cause auroras instead of atomic nitrogen?

**Tags:** atmosphere, upper-atmosphere, auroras

> **Comments:**
> **username_1**: The first aurora I saw in the southern hemisphere was a red aurora. However, I haven't seen many auroras down here.  
> **username_2**: Don't forget that human eyes are more sensitive to green than to red, and in low-light conditions even more to cyan than to green. So red auroras might be frequent but not bright enough to see.  
> **username_0**: To username_1, where are you located?  
> **username_0**: To username_2, Why are we more sensitive to green light when 65% of our cone cells are red cone cells?  
> **username_3**: Atoms or molecules of anything up there cause auroras. The question is, which sources give results that land in our visible frequency range?  

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## 1 answers

### Answer by username_3 on 2022-02-27. Score: 1

In fact multiple species of oxygen or nitrogen can create emissions at various wavelengths. There can be aurorae over a wide range of wavelengths, we just see only some of them that happen to be in the visible range. So, it's all a matter of which species hit the relatively narrow visible target.

With respect to oxygen, Rezaei et al. [1](https://i.sstatic.net/3qmbT.png) provide this spectrum, in which atomic oxygen produces an emission near the red end of the visible range, while ions of both monatomic and diatomic oxygen give less intense emissions of various colors from blue to orange. Note that no emission is listed for neutral $\text{O}\_2$.

[![enter image description here](https://i.sstatic.net/3qmbT.png)](https://i.sstatic.net/3qmbT.png)

With nitrogen, similar results from Hosseini et al. [2](https://i.sstatic.net/SPos8.png) show an emission in the violet or blue range from ionized diatomic nitrogen, but none from any monatomuc nitrogen species. Note that in this spectrum the red eemission from atomic oxygen is seen, apparently from a small amount of this imputity in the gas sample.

[![enter image description here](https://i.sstatic.net/SPos8.png)](https://i.sstatic.net/SPos8.png)

**References**

1.
Rezaei, Fatemeh & Abbasi-Firouzjah, Marzieh & Shokri, Babak (2014). "Investigation of antibacterial and wettability behaviours of plasma-modified PMMA films for application in ophthalmology", *Journal of Physics D Applied Physics*, **47**, 085401. <https://doi.org/10.1088/0022-3727/47/8/085401>.

2.
Hosseini, Seyed Iman & Mohsenimehr, Soad & Hadian, Javad & Ghorbanpour, Mansour & Shokri, Babak (2018). "Physico-chemical induced modification of seed germination and early development in artichoke ( Cynara scolymus L.) using low energy plasma technology", *Physics of Plasmas*, **25**, 013525. <https://doi.org/10.1063/1.5016037>.

> **Comments:**
> **username_1**: How are your two answers different? Why not just edit the first answer if you wanted to add, remove or clarify something?  
> **username_3**: Sorry, it was an accident. Will delete the other one.  

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