"What I wrote is that there must be a definite article in front of 'solar', the verb has to be conjugated according to the subject and again another article before 'solar'."
Gnomeo, do you agree with this? Is it about specific solar activity known to the writer and reader, or is it a general statement about all solar activity?
I disagree with george_mnt, because the statement is clearly about solar activity in general. I think that he has been confused by the definite article used in the Bulgarian version.