Translation:We are reading about chemical reaction processes on the surface of the Sun.
I think most scientists would say that the surface of the sun is way too hot to have any chemical reactions. What occurs on the surface of the sun are nuclear reactions. So if you replace chemical with nuclear, the sentence would make more sense.
Does "reaksi kimia" definitely only refer to what are technically known as chemical reactions?
I do want to point out that even if it's not factually correct, it is a valid sentence that someone (however ill informed) might say.
A chemical reaction is a process, so "chemical reaction processes" is redundant.
It's valid in english to say "Process of chemical reactions" which I believe is the intended meaning.
I agree it is redundant but may not be gramatically wrong. A 'process' is inherent in the definition of 'chemical process'.