I know that aurorae are caused by solar activity interacting with the Earth's magnetic field as charged particles are funneled down into the polar magnetic mirrors.

On one hand, I know that as charged particles accelerate, they will produce radiation. They will happen in at least two ways in the context of aurorae:

  1. Charged particles will gyrate around magnetic field lines with a characteristic frequency, which presumably varies with pitch angle and position in Earth's magnetic field.
  2. As the charged particles are slowed down by the magnetic mirror effect, they will release some radiation.

I've also heard that the visible radiation is caused by re-radiation from oxygen or nitrogen atoms which have been excited by collisions with these charged particles.

Which effects cause radiation at which wavelengths/frequencies, and what actually causes the visible aurorae?

  • $\begingroup$ Aren't these the spirits of the dead dancing in the night sky? $\endgroup$ – Gimelist Jan 24 '16 at 1:49
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    $\begingroup$ jvriesem: How much do you know about atomic phyiscs? If you understand how quantum transitions work, the answer to your question is straightforward textbook science... $\endgroup$ – AtmosphericPrisonEscape Jan 24 '16 at 17:43
  • $\begingroup$ @AtmosphericPrisonEscape: I have a M.Sc. in Physics and another in Planetary Science. I understand quantum mechanics, energy levels, transitions, and so on at the atomic and molecular level. Among my areas of interest are plasma physics and atmospheric dynamics. I know the basics, but it's the advanced stuff I'm still wondering about. $\endgroup$ – jvriesem Jan 26 '16 at 22:45
  • $\begingroup$ @jvriesem: And this was too hard to google? $\endgroup$ – AtmosphericPrisonEscape Jan 26 '16 at 23:19
  • $\begingroup$ @AtmosphericPrisonEscape: Haha, I guess so! :-) I did search for it online for quite a while, but I was finding only intro-level material or dense research papers—nothing in between. The intro level material for the general public lacked the depth I needed, and the research papers lacked the summary I wanted to see. $\endgroup$ – jvriesem Jan 26 '16 at 23:22

When the solar wind is funneled into the Earth's magnetic poles, those particles excite the electrons of molecules in the atmosphere which then bumps those electrons up into another orbital. When the electrons fall back down into their native orbital, they produce a photon of a particular wavelength whose energy is equal to the difference between the energy states of the two orbitals.

There is a good pdf from NASA here and another good article here.

  • $\begingroup$ Accepted for the second referenced article in particular, since it explained the details of the transitions and gave the wavelengths. Thanks! $\endgroup$ – jvriesem Jan 26 '16 at 22:47

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