Prospects for extragalactic particles from exotic processes

Necessary prerequisites for examining the prospects for exotic processes gi ving rise to extragalactic particles are the mass composition and the deter mination of the cosmic ray energy above which the majority of the particles are of extragalactic origin. Both aspects are examined here. It is argued that 3 x 10(18) eV represents the demarkation energy above which the fracti on of extragalactic particles rises rapidly. It is also argued that the mass composition remains mixed at the highest en ergies. The latter fact, coupled with the less-than-expected anisotropy of arrival directions, indicates that exotic processes are not responsible for the extragalactic flux.