Would you prefer for them to be referred to them as "Cosmic Rays" :) ? To be honest, "Space Particles" sounds less silly and more descriptive. It also emphasizes that they're not generating the muons themselves, but collecting them from space.
EDIT: Though I guess, now that I think of it, it's a bit unfair to refer to muons as 'exotic'. People will typically encounter thousands of them in a day [1].
Yeah, of course! They are cosmic ray muons after all, as in "muons created by cosmic rays". The words "space particles" is more correctly applied to dust (the type in space obvs.) and stuff like that in my opinion.
Honestly "space particle" to me sounds to be the same sort of suspect phrase as "space pen".
Well, yes; but calling them "exotic-in-the-sense-we-don't-talk-about-them-very-much-even-though-they-pass-by-all-the-time-that-got-created-when-an-actual-space-particle-that-wasn't-that-exotic-like-a-proton-or-helium-atom-hit-the-atmosphere particles called muons" doesn't quite roll off the tongue. :)
They ultimately (and not in the we're all space dust sense, more like 2.2 microseconds ago sense) are caused by interactions with particles from outer space, so calling them space particles, isn't that bad. :) But yeah; it's does elide that aspect of them.
EDIT: Though I guess, now that I think of it, it's a bit unfair to refer to muons as 'exotic'. People will typically encounter thousands of them in a day [1].
[1] http://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm
[1] "Muons arrive at sea level with an average flux of about 1 muon per square centimeter per minute."