the sun - Source of high energy cosmic particles

Earth receives shower of both solar and cosmic radiations every seconds. The Sun put up a heliosphere around the solar system and thus foreign high energy charged particles could not penetrate easily. Is there any other source most probably that lies within our solar system?

Note:

1. Very high energy cosmic particle beyond 5.7 x 10^19 eV were observed
   by Pierre Auger Observatory in Argentina. (rare but the GZK limit
   seems to rule out distance sources)


2. GZK limit roughly capped the upper energy level of cosmic ray as
   they are slowed due to CMB over vast distance