I came across this beautiful animation of the auroras on Saturn. The auroras are caused by charged particles (ions) from the sun, the solar wind of protons and electrons, are focused down onto areas near the poles of a planet by the magnetic lines of a planet’s magnetic field. The ions hit the atmosphere colliding with atmospheric gas molecules like nitrogen and oxygen causing them to become excited and spit out electrons (becoming ions themselves). Molecules are not “happy” when they’re missing electrons so they’ll capture one to become “fulfilled” (fill their outer electron shells). It’s when they recapture electrons that they give off the light that we see as the auroras.
On Earth the auroras are green or brownish-red (from the Oxygen) and blue or red (from the Nitrogen). Saturn’s atmosphere is mostly hydrogen and helium so we’re not quite sure what color its auroras are. The auroras in the animation were colored in by NASA since the camera on the Cassini spacecraft is black and white.
The video clip below gives a nice explanation of auroras.