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?

  • $\begingroup$ The first aurora I saw in the southern hemisphere was a red aurora. However, I haven't seen many auroras down here. $\endgroup$
    – Fred
    Sep 22 at 17:04
  • $\begingroup$ 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. $\endgroup$
    – Ruslan
    Sep 23 at 13:23
  • $\begingroup$ To Fred, where are you located? $\endgroup$
    – Lisa Baron
    Sep 28 at 2:52
  • $\begingroup$ To Ruslan, Why are we more sensitive to green light when 65% of our cone cells are red cone cells? $\endgroup$
    – Lisa Baron
    Sep 28 at 2:53
  • $\begingroup$ Atoms or molecules of anything up there cause auroras. The question is, which sources give results that land in our visible frequency range? $\endgroup$ Oct 5 at 16:24

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