Actually, there is another flaw in the sentence, and perhaps a more serious one. Maybe, both stream and streaming are fine. Both phrases
continuous stream of particles, and
continuous streaming of particles behave as nouns and make sense.
Here's the real flaw -
Besides heat and light, the sun is also the source of .......
The sentence as above is ambiguous. It could be interpreted as -
Heat and light are the source of continuous stream....and besides heat and light, sun is also the source of continuous stream....
The above could be inferred from the sentence as written, and is clearly not the intended meaning of the sentence.
Besides heat and light, the sun..... - heat, light and sun are treated as equivalent.
To convey the intended meaning unambiguously, it could have been written as --
Besides being the source of heat and light, the sun is also the source of....... -> Although awkward, this sentence now is unambiguous. In this structure the phrase before comma correctly modifies the sun. In the original form (choice C), besides heat and light does not modify the sun.