Understanding the effects of geometry and rotation on pulsar intensity profiles

TL;DR

This paper presents a comprehensive method to model pulsar radio emission profiles by considering geometry and rotation, revealing how these factors influence observed asymmetries and profile features.

Contribution

The authors develop a novel computational approach to simulate pulsar emission regions and profiles, incorporating rotation effects and curvature radiation mechanisms.

Findings

Rotation causes significant asymmetries in radio profiles.

Emission heights vary across field lines, affecting profile shape.

The model explains core emission and one-sided cone observations.

Abstract

We have developed a method to compute the possible distribution of radio emission regions in a typical pulsar magnetosphere, taking into account the viewing geometry and rotational effects of the neutron star. Our method can estimate the emission altitude and the radius of curvature of particle trajectory as a function of rotation phase for a given inclination angle, impact angle, spin-period, Lorentz factor, field line constant and the observation frequency. Further, using curvature radiation as the basic emission mechanism, we simulate the radio intensity profiles that would be observed from a given distribution of emission regions, for different values of radio frequency and Lorentz factor. We show clearly that rotation effects can introduce significant asymmetries into the observed radio profiles. We investigate the dependency of profile features on various pulsar parameters. We find that the radiation from a given ring of field lines can be seen over a large range of pulse longitudes, originating at different altitudes, with varying spectral intensity. Preferred heights of emission along discrete sets of field lines are required to reproduce realistic pulsar profiles, and we illustrate this for a known pulsar. Finally, we show how our model provides feasible explanations for the origin of core emission, and also for one-sided cones which have been observed in some pulsars.