Auroras, also known as northern and southern (polar) lights or aurorae (singular: aurora), are natural light displays in the sky, particularly in the polar regions, and usually observed at night. They typically occur in the ionosphere. They are also referred to as polar auroras. This is a misnomer however, because they are commonly visible between 65 to 72 degrees north and south latitudes, which place them a ring just within the Arctic and Antarctic circles. Aurorae do occur deeper inside the polar regions, but these are infrequent and often invisible to the naked eye.
In northern latitudes, the effect is known as the aurora borealis, named after the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas, by Pierre Gassendi in 1621. The aurora borealis is also called the northern polar lights, as it is only visible in the sky from the Northern Hemisphere, with the chance of visibility increasing with proximity to the North Magnetic Pole. (The North Magnetic Pole is currently in the arctic islands of northern Canada.) Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the Sun were rising from an unusual direction. The aurora borealis most often occurs near the equinoxes. The northern lights have had a number of names throughout history. The Cree call this phenomenon the "Dance of the Spirits." In Europe, in the Middle Ages, the auroras were commonly believed a sign from God (see Wilfried Schröder, Das Phänomen des Polarlichts, Darmstadt 1984).
Its southern counterpart, the aurora australis or the southern polar lights, has similar properties, but is only visible from high southern latitudes in Antarctica, South America, or Australasia. Australis is the Latin word for "of the South."
Auroras can be spotted throughout the world and on other planets. They are most visible closer to the poles due to the longer periods of darkness and the magnetic field.