NASA unveils greatest views of the aurorae ever, from space in HD
“When the free electrons finally find the ions they bind to, they drop down in energy, creating an incredible display of colorful possibilities. Of all of them, it’s the oxygen (mostly, with the strong emission line at 558 nanometers) and the nitrogen (secondary, with the smaller line at a slightly higher wavelength) that create the familiar, spectacular green color we most commonly associate with aurorae, but blues and reds — often at higher altitudes — are sometimes possible, too, with contributions from all three of the major atmospheric elements and their combinations.”
The northern (aurora borealis) and southern (aurora australis) lights are caused by a combination of three phenomena on our world, that make our aurorae unique among all worlds in our solar system:
Outbursts from the Sun that can go in any direction,
Our magnetic field, that funnels charged particles into circles around the poles,
And our atmospheric composition, that causes the colors and the displays we see.