Nulls subpulse drift and mode-switching in pulsars: the polar-cap surface

TL;DR

This paper explores how the physical states of pulsar polar caps influence phenomena like nulls, subpulse drift, and mode-switching, emphasizing the role of charge separation and Langmuir-mode turbulence in pulsar emission behavior.

Contribution

It introduces a model linking polar-cap physical states and charge separation processes to complex pulsar emission phenomena, offering new explanations for nulls, subpulse drift, and mode-switching.

Findings

Charge separation limits acceleration potential at polar caps.

Langmuir-mode turbulence couples with radiation, affecting pulsar signals.

Different physical states of the polar cap can explain observed pulsar phenomena.

Abstract

Little attention has so far been paid to the division of the observed population between pulsars of the two spin directions that are possible. Almost all pulsars with positive corotational charge density at the polar caps are expected to satisfy space-charge limited flow boundary conditions. Charge separation by blackbody photo-electric transitions in moving ions limits the acceleration potential, analogously with the more usually considered pair creation. But the limitation is more severe so that proton and ion energies can be relativistic but not ultra-relativistic, and these allow the growth of Langmuir-mode induced turbulence that couples directly with the radiation field, as shown by Asseo, Pelletier & Sol. The consequences of this, and of the several possible physical states of the polar cap, are described, qualitatively, as possible explanations for the complex phenomena of nulls, subpulse drift and mode-switching observed in subsets of pulsars.