Rapid Modification of Neutron Star Surface Magnetic Field: A proposed mechanism for explaining Radio Emission State Changes in Pulsars

TL;DR

This paper proposes a mechanism involving Hall drift and thermoelectric effects that rapidly modify the neutron star's surface magnetic field, explaining the quasi-periodic radio emission state changes observed in pulsars.

Contribution

It introduces a novel model combining Hall drift and thermoelectric oscillations to account for pulsar radio emission variability through surface magnetic field modifications.

Findings

Hall drift causes faster magnetic field changes than Ohmic decay and thermoelectric effects.

The proposed mechanism links magnetic field perturbations to observed emission state changes.

Surface magnetic field evolution timescales align with pulsar emission variability periods.

Abstract

The radio emission in many pulsars show sudden changes, usually within a period, that cannot be related to the steady state processes within the inner acceleration region (IAR) above the polar cap. These changes are often quasi-periodic in nature, where regular transitions between two or more stable emission states are seen. The durations of these states show a wide variety ranging from several seconds to hours at a time. There are strong, small scale magnetic field structures and huge temperature gradients present at the polar cap surface. We have considered several processes that can cause temporal modifications of the local magnetic field structure and strength at the surface of the polar cap. Using different magnetic field strengths and scales, and also assuming realistic scales of the temperature gradients, the evolutionary timescales of different phenomena affecting the surface magnetic field was estimated. We find that the Hall drift results in faster changes in comparison to both Ohmic decay and thermoelectric effects. A mechanism based on the Partially Screened Gap (PSG) model of the IAR has been proposed, where the Hall and thermoelectric oscillations perturb the polar cap magnetic field to alter the sparking process in the PSG. This is likely to affect the observed radio emission resulting in the observed state changes.