Determine the source of the Crab pulsar’s narrow-band pump wave

Determine the physical source of the strong, narrow-band, linearly polarized pump wave responsible for the Crab pulsar’s zebra-like emission pattern.

Background

The paper compares the Crab pulsar’s stable, linearly polarized, approximately proportionally spaced emission bands with the spectral pattern generated when an ordinary-like axion-conversion wave drives a parametric plasma instability. The observed pattern suggests that some strong, narrow-band, linearly polarized wave is acting as a pump for a parametric instability.

The paper does not identify whether this pump is produced by axion-induced conversion or by conventional plasma astrophysics. Consequently, the physical origin of the pump remains unresolved and must be determined before the Crab spectrum can be connected to the proposed axion mechanism.