From: Bob Cook * * Muons appear in Cosmic rays AFAIK. They must be relativistic to exist as long as it take to travel from the Sun to Earth, given their low energy decay rate at non-relativist energies. Cosmic ray muons would be even more relativistic with longer apparent lifetimes. Muons are actually made in Earth’s atmosphere from Cosmic ray impact with air. They aren’t coming from the Sun.
Wiki sez: About 10,000 muons reach every square meter of the earth's surface a minute; these charged particles form as by-products of cosmic rays colliding with molecules in the upper atmosphere. Traveling at relativistic speeds, muons can penetrate tens of meters into rocks and other matter before attenuating as a result of absorption or deflection by other atoms.[5] <https://en.wikipedia.org/wiki/Muon>
