Mon. Not. R. Astron. Soc., 470, 4307-4329 (2017/October-1)
Radio pulsar glitches as a state-dependent Poisson process.
FULGENZI W., MELATOS A. and HUGHES B.D.
Abstract (from CDS):
Gross-Pitaevskii simulations of vortex avalanches in a neutron star superfluid are limited computationally to <=102 vortices and <=102 avalanches, making it hard to study the long-term statistics of radio pulsar glitches in realistically sized systems. Here, an idealized, mean-field model of the observed Gross-Pitaevskii dynamics is presented, in which vortex unpinning is approximated as a state-dependent, compound Poisson process in a single random variable, the spatially averaged crust-superfluid lag. Both the lag-dependent Poisson rate and the conditional distribution of avalanche-driven lag decrements are inputs into the model, which is solved numerically (via Monte Carlo simulations) and analytically (via a master equation). The output statistics are controlled by two dimensionless free parameters: α, the glitch rate at a reference lag, multiplied by the critical lag for unpinning, divided by the spin-down rate; and β, the minimum fraction of the lag that can be restored by a glitch. The system evolves naturally to a self-regulated stationary state, whose properties are determined by α/αc(β), where αc(β) ≃ β–1/2 is a transition value. In the regime α >= αc(β), one recovers qualitatively the power-law size and exponential waiting-time distributions observed in many radio pulsars and Gross-Pitaevskii simulations. For α ≪ αc(β), the size and waiting-time distributions are both power-law-like, and a correlation emerges between size and waiting time until the next glitch, contrary to what is observed in most pulsars. Comparisons with astrophysical data are restricted by the small sample sizes available at present, with <=35 events observed per pulsar.
© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
stars: neutron - pulsars: general - stars: rotation - stars: rotation
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