Interpretation of the Low-Frequency Peculiarities in the Radio Profile Structure of the Crab Pulsar

TL;DR

This paper develops a theory of magnetized induced scattering in pulsar magnetospheres, explaining low-frequency features in the Crab pulsar's radio profile through harmonic scattering and polarization data.

Contribution

It introduces a novel scattering model explaining low-frequency profile features and predicts similar transient components in other pulsars.

Findings

Scattering from the first harmonic explains the Crab pulsar's low-frequency component.

Induced scattering accounts for the precursor component observed.

Polarization data strongly supports the proposed scattering mechanisms.

Abstract

The theory of magnetized induced scattering off relativistic gyrating particles is developed. It is directly applicable to the magnetosphere of a pulsar, in which case the particles acquire gyration energies as a result of resonant absorption of radio emission. In the course of the radio beam scattering into background the scattered radiation concentrates along the ambient magnetic field. The scattering from different harmonics of the particle gyrofrequency takes place at different characteristic altitudes in the magnetosphere and, because of the rotational effect, gives rise to different components in the pulse profile. It is demonstrated that the induced scattering from the first harmonic into the state under the resonance can account for the so-called low-frequency component in the radio profile of the Crab pulsar. The precursor component is believed to result from the induced scattering between the two states well below the resonance. It is shown that these ideas are strongly supported by the polarization data observed. Based on an analysis of the fluctuation behaviour of the scattering efficiencies, the transient components of a similar nature are predicted for other pulsars.