Overview
Aurora is an atmospheric phenomenon that can be observed near the polar regions. Also called polar light.
The solar wind that is drawn toward the Earth from the Sun collides with atoms in the Earth's atmosphere, producing light and creating auroras. Since it occurs far above the earth's surface, about 100km or more above the ground, it requires clear skies with no clouds to be able to observe it.
By the way, in works of fiction, it is often depicted as having seven colors like a rainbow, but in reality, it often appears as white or green like a cloud.