Answer:
Initially energy is in the form of Radiations
Explanation:
Sun is made up of gases in which major proportion is hydrogen gas.
Here we know that surface of sun is vert hot and its temperature is very large
So due to this high temperature hydrogen gas combined and form helium nuclei, this change in the nuclei reaction is known as nuclear reaction.
In this nuclear reaction we can see that two light nuclei will combine and form a big stable nuclei. This type of reaction is known as nuclear fusion and energy released in this type of nuclear fusion is always in form of gamma radiations.
Now these gamma radiations are absorbed by other charged particles and those charged particles are then accelerated to higher energy.
So initial form of this energy is Gamma Radiations