Aurora Aurora is a natural display of light in the sky that can be seen with the unaided eye only at night. An auroral display in the Northern Hemisphere is called the aurora borealis, or the northern lights. A similar phenomenon in the Southern Hemisphere is called the aurora australis. Auroras are the most visible effect of the sun's activity on the earth's atmosphere.
Most auroras occur in far northern and southern regions.
They appear chiefly as arcs, clouds, and streaks. Some move, brighten, or flicker suddenly. The most common color in an aurora is green. But displays that occur extremely high in the sky may be red or purple. Some extend lengthwise across the sky for thousands of miles or kilometers.