The Sun is the Creator, Preserver and destroyer and takes the three forms of "BRAMHA", "VISHNU", and "RUDRA". Hence the Sun symbolizing godhead is said to be Omniscient (all seeing / knowing Brahma), Omnipresent (Present everywhere and preserving Shri Vishnu) and Omnipotent (all-powerful like Lord Shiva). Thus the Sun becomes the "Ayana" (direction) of the Nara (humans) and is called "Narayana" (God).
Depending upon the direction of one's chief activity in life, the human beings can be classified as :
Brahamins (Seeking knowledge i.e. Teachers, Priests etc.)
Kshatriyas (Protectors i.e. Police, Military)
Vaishayas (Preservers i.e. Businessmen,)
Shudras (Involved in Labors)
Since the 10th house governs "Karma" the "DasAkshari" (10 lettered) Mantra of the Sun God helps one to achieve success in his career / profession and in one's endeavour.
The three mantras for BRAHMINS / KSHTRIYAS / VAISHAYAS are as follows :
Brahmins :- OM HRIM GHRINI SURYAADITYA OM
Kshatriyas :- OM HRIM GHRINI SURYAADITYA AIM
Vaishyas :- OM HRIM GHRINI SURYAADITYA AIM
For All :- OM GHRINI SURYAADITYAH