Filling the Magnetospheres of Weak Pulsars

TL;DR

This paper explores how weak pulsars fill their magnetospheres without relying on outer magnetosphere pair creation, revealing a new quasi-periodic solution that may explain pulsar death lines and emission patterns.

Contribution

It introduces self-consistent magnetosphere solutions for weak pulsars that do not depend on pair creation at the light cylinder, including a novel quasi-periodic state.

Findings

Quasi-periodic magnetosphere solutions with half-rotation period cycles.

Weak pulsars can sustain magnetospheres without outer pair production.

Potential explanation for pulsar death line and emission patterns.

Abstract

Recent advances in numerical algorithms and computational power have enabled first-principles simulations of pulsar magnetospheres using Particle-in-Cell (PIC) techniques. These ab-initio simulations seem to indicate that pair creation through photon-photon collision at the light cylinder is required to sustain the pulsar engine. However, for many rotation-powered pulsars pair creation operates effectively only near the stellar surface where magnetic field is high. How these "weak pulsars" fill their magnetospheres without efficient photon-photon pair conversion in the outer magnetosphere is still an open question. In this paper, we present a range of self-consistent solutions to the pulsar magnetosphere that do not require pair production near the light cylinder. When pair production is very efficient near the star, the pulsar magnetosphere converges to previously-reported solutions. However, in the intermediate regime where pair supply is barely enough to sustain the magnetospheric current, we observe a time-dependent solution with quasi-period about half of the rotation period. This new quasi-periodic solution may explain the observed pulsar death line without invoking multipolar components near the star, and can potentially explain the core vs. conal emission patterns observed in pulsar radio signals.