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

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 ( P ̇ ), dispersion measure, and radio flux density—using accurate high-dimensional Kolmogorov–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.