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:
- 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.
- 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?