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

TL;DR

This paper critically examines a proposed pulsar-supernova interaction mechanism for the cosmic ray knee, concluding that it is unlikely to be a common explanation due to the extreme conditions required.

Contribution

It provides a detailed analysis of the pulsar-supernova interaction model and demonstrates its implausibility for explaining the cosmic ray knee with known astrophysical objects.

Findings

The mechanism requires highly unusual pulsar-supernova conditions.

It is unlikely that known pulsar-supernova systems can produce the knee.

The proposed model does not convincingly explain the spectral feature.

Abstract

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