We consider the energy spectrum of cosmic-rays ( CRs ) from a purely phenomenological point of view and investigate the possibility that they all be produced by the same type of sources with a single power-law spectrum , in E ^ { - x } , from thermal to ultra-high energies .
We show that the relative fluxes of the Galactic ( GCR ) and extra-galactic ( EGCR ) components are compatible with such a holistic model , provided that the index of the source spectrum be x \simeq 2.23 \pm 0.07 .
This is compatible with the best-fit indices for both GCRs and EGCRs , assuming that their source composition is the same , which is indeed the case in a holistic model .
It is also compatible with theoretical expectations for particle acceleration at relativistic shocks .