Sun dogs appear over the horizon in Siziwang Banner, Ulaanqab, Inner Mongolia autonomous region, on Jan 9, 2018. A sun dog, sometimes called a parhelion or mock sun, is a member of the halo family and is caused by the refraction of sunlight by ice crystals in the atmosphere. Sun dogs typically appear as a pair of subtly colored patches of light at the same altitude above the horizon as the sun. Sun dogs are best seen and most conspicuous when the Sun is near the horizon. [Photo/Xinhua]