An aurora is an astronomical phenomenon, when colored lights seem to shimmer in the sky. Auroral refers to that display––you might describe it as a show of auroral light.
The best known aurora is the aurora borealis, otherwise known as the northern lights. If you ever have trouble with auroral, try to remember Fozzie Bear's summation of the impossible from a line in the "Muppet Movie": "The aurora borealis/shining down in Dallas/Can you picture that?"
