The term exaltation is part of traditional astrology in classifying planets. Exaltation is a sign placement said to be more favourable. The Sun in Leo has dignity in it's own sign, and Sun in Aries is a more potent force for self expression. The Sun is consciousness, so often reflected in the Sun suggests the power of choice, to creative and apply those energies to living.
Helios, Apollo, Sol, or the Sun, is the center and the source of all things in our system. As Evangeline Evans says, by him are all things and in him all things subsist. For each one of us we are the central figure of a drama divine. The Sun is the chief source of energy. The Sun's gravity keeps the planets in orbit and also dictates their speeds. The closer they are to the Sun, the faster they go. The Sun in the human being represents the consciousness that returns every morning after sleep. In Aries it is the awakening to a new day of possibility and the feeling of being of alive.
The Sun is what we crate for ourselves and it is what we go out and do independently alone, we build our life and it is what we have created and even if we don't like what has been made it still belongs to us.