Pulsar Population Synthesis with Magnetorotational Evolution: Constraining the Decay of Magnetic field

TL;DR

This paper develops a pulsar population model incorporating magnetic field decay and magnetorotational evolution, fitting observed data to constrain decay timescales and dominant decay processes.

Contribution

It introduces a comprehensive population synthesis model with magnetic field decay, favoring an exponential decay scenario driven by ohmic dissipation, supported by observational data fitting.

Findings

Exponential magnetic field decay model fits pulsar data better.

Decay timescale is approximately 8.3 million years.

Ohmic dissipation likely dominates magnetic field decay in aged pulsars.

Abstract

We present a population synthesis model for normal radio pulsars in the Galaxy incorporating the latest developments in the field and the magnetorotational evolution processes. Our model considers spin-down with a force-free magnetosphere and the decay of the magnetic field strength and its inclination angle. The simulated pulsar population is fit to a large observation sample that covers the majority of radio surveys using the Markov Chain Monte Carlo technique. We compare the distributions of four major observables: spin period (P), spin down rate($\dot{P}$), dispersion measure, and radio flux density using accurate high-dimensional Kolmogoro-Smirnov statistics. We test two B-field decay scenarios, an exponential model motivated by ohmic dissipation and a power-law model motivated by the Hall effect. The former clearly provides a better fit, and it can successfully reproduce the observed pulsar distributions with a decay timescale of $8.3_{-3.0}^{+3.9}$ Myr. The result suggests that significant B-field decay in aged pulsars and ohmic dissipation could be the dominant process.