Interesting, thanks for clarifying.

Perhaps I'm biased by my own ignorance, but the speed of sound in the solar wind (or the fact that terms like "speed of sound" still make sense in an ostensible vacuum) seems like the sort of thing a reasonable person might not know. If science writing is to be accessible to the layperson, an explanatory parenthetical (even just clarifying the approximate speed at which the subsonic wind was traveling) would have been helpful.

Thanks for the downvote, though.

I absolutely didn't downvote you, I fully agree with your point, and was equally confused by the use those terms in that context.