Why is ozone formed over the equator ? What is the connection between sunlight and ozone formation ?

Ozone is formed everywhere, not only over the equator. However, since ozone is formed when ultraviolet light hits oxygen molecules in the upper atmosphere (making it reactive and thus capable of reacting with other oxygen to form ozone molecules), it would be forming at a higher rate where there is more light. Since the tropical regions get more direct sunlight, and thus more UV light, the rate of production of ozone is higher there than under more northern or southern regions, where sunlight is not as intense.