It can be used in a variety of contexts, such as:

* Solar energy: Energy derived from the sun's radiation.

* Solar system: The collection of planets and other celestial bodies that orbit the sun.

* Solar eclipse: An event where the moon passes between the sun and Earth, blocking out the sun's light.

* Solar flare: A sudden burst of energy from the sun's surface.

There is no direct connection between Arthur becoming King and the term "solar." Perhaps you're thinking of something else?

Could you please provide more context or clarify your question?