On the Nature of Precursors in the Radio Pulsar Profiles

TL;DR

This paper proposes a physical model explaining the precursor component in radio pulsar profiles as a result of induced scattering of the main pulse radiation, accounting for its polarization, spectral, and fluctuation properties.

Contribution

It introduces a novel scattering-based mechanism for the precursor phenomenon in pulsars, linking it to the main pulse through a specific physical process.

Findings

The precursor is explained as scattered radiation directed along magnetic fields.

The model accounts for high linear polarization and spectral features of precursors.

It suggests a connection between precursor and main pulse across frequencies.

Abstract

In the average profiles of several radio pulsars, the main pulse is accompanied by the preceding component. This so called precursor is known for its distinctive polarization, spectral, and fluctuation properties. Recent single-pulse observations hint that the sporadic activity at the extreme leading edge of the pulse may be prevalent in pulsars. We for the first time propose a physical mechanism of this phenomenon. It is based on the induced scattering of the main pulse radiation into the background. We show that the scattered component is directed approximately along the ambient magnetic field and, because of rotational aberration in the scattering region, appears in the pulse profile as a precursor to the main pulse. Our model naturally explains high linear polarization of the precursor emission, its spectral and fluctuation peculiarities as well as suggests a specific connection between the precursor and the main pulse at widely spaced frequencies. This is believed to stimulate multifrequency single-pulse studies of intensity modulation in different pulsars.