Literary and poetic; you'd see it in song lyrics, poems, and scenic description but rarely in everyday speech, where 太阳 'sun' is the default.
culture
Strongly associated with sunrise and sunset imagery. In older songs about Chairman Mao (毛泽东) the sun is an image for him: 《东方红》 'The East Is Red' opens with the rising sun, and he was often called 红太阳 'the red sun'.
