A sun dog or sundog, scientific name parhelion (plural parhelia) from Greek παρήλιον (parēlion), meaning “beside the sun”; from παρά (para), meaning “beside”, and ἥλιος (helios), meaning “sun”, also called a mock sun or a phantom sun, is an atmospheric phenomenon that creates bright spots of light in the sky, often on a luminous ring or halo on either side of the sun.

http://en.wikipedia.org/wiki/Sun_dog