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The origin of the prominent 'knee' in the cosmic ray energy spectrum at anenergy of several PeV is still uncertain. A recent mechanism has shown promise,however; this involves particles from a very young pulsar interacting with theradiation field from a very young supernova remnant. The ensuing nuclearreaction of the particles with the photons by way of e+e- production thencauses the characteristic knee. In an earlier paper we argued that themechanism would imply only one source of a very rare type - if it were toexplain the spectral shape. Here we examine the mechanism in more detail andconclude that for even a single source to work its characteristics would needto be so unusual that the mechanism would not be possible for any known type ofpulsar-supernova combination.

The knee in the cosmic ray energy spectrum: a pulsar/supernova origin?