High Frequency Cutoff and Change of Radio Emission Mechanism in Pulsars

TL;DR

This paper introduces a new theoretical model explaining the high-frequency cutoff in pulsar radio spectra, linking it to electron acceleration in the polar gap and predicting its dependence on pulsar period and magnetic field.

Contribution

It proposes a novel mechanism for pulsar radio emission occurring in the polar gap, providing explanations for spectral cutoff dependence on pulsar parameters.

Findings

The model explains the observed high-frequency cutoff dependence on pulsar period.

It predicts the cutoff position's relation to magnetic field strength.

The approach estimates the radio emission power consistent with observations.

Abstract

Pulsars are the fast rotating neutron stars with strong magnetic field, that emit over a wide frequency range. In spite of the efforts during 40 years after the discovery of pulsars, the mechanism of their radio emission remains to be unknown so far. We propose a new approach to solving this problem for a subset of pulsars with a high-frequency cutoff of the spectrum from the Pushchino catalogue (the "Pushchino" sample). We provide a theoretical explanation of the observed dependence of the high-frequency cutoff from the pulsar period. The dependence of the cutoff position from the magnetic field is predicted. This explanation is based on a new mechanism for electron radio emission in pulsars. Namely, radiation occurs in the inner (polar) gap, when electrons are accelerated in the electric field that is increasing from zero level at the star surface. In this case acceleration of electrons passes through a maximum and goes to zero when the electron velocity approaches the speed of light. All the radiated power is located within the radio frequency band. The averaging of intensity radiation over the polar cap, with some natural assumptions of the coherence of the radiation, leads to the observed spectra. It also leads to an acceptable estimate of the power of radio emission.