The Sun is the source of all energies. These energies stimulate the activities of the houses occupied by the transiting Sun and reinforce or weaken the planetary effects, depending on the Sun's aspect to the natal planet. When the Sun transits an inner planet, it may trigger a dormant aspect between that inner planet and a slower moving outer planet. If a planet is being transited by another planet when it is being transited by the Sun, the effect of the transit is strengthened.
Sun Sextile Mercury
A Sun sextile Mercury aspect shows that you value and encourage your partners thoughts and ideas and are very open to supporting their intellectual progress. You like to talk with one another and find it easy and enjoyable to exchange concepts and information. When the Sun person is sextile to the Mercury person, your partner is open to any request which will further your intellectual growth, and is stimulated by your ideas and conversations. It favors intellectual friendships and cooperation. It is good for teamwork where communication of ideas and practical know how is important. Your ability to communicate well enables you to resolve problems easily.