Avalanche Dynamics of Radio Pulsar Glitches

By Andrew Melatos, C. Peralta, J. Stuart B. Wyithe. 2007

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We test statistically the hypothesis that radio pulsar glitches result from an avalanche process, in which angular momentum is transferred erratically from the flywheel-like superfluid in the star to the slowly decelerating, solid crust via spatially connected chains of local, impulsive, threshold-activated events, so that the system fluctuates around a self-organized critical state. Analysis of the glitch population (currently 285 events from 101 pulsars) demonstrates that the size distribution in individual pulsars is consistent with being scale invariant, as expected for an avalanche process. The measured power-law exponents fall in the range -0.13 ⩽ a⩽ 2.4, with a ≈ 1.2 for the youngest pulsars. The waiting-time distribution is consistent with being exponential in seven out of nine pulsars where it can be measured reliably, after adjusting for observational limits on the minimum waiting time, as for a constant-rate Poisson process. PSR J0537–6910 and PSR J0835–4510 are the exceptions; their waiting-time distributions show evidence of quasi-periodicity. In each object, stationarity requires that the rate λ equal −ϵν̇/⟨Δν⟩, where ν̇ is the angular acceleration of the crust, ⟨ Δ ν ⟩ is the mean glitch size, and ϵν̇ is the relative angular acceleration of the crust and superfluid. Measurements yield ϵ ⩽ 7 × 10−5 for PSR J0358+5413 and ϵ ⩽ 1 (trivially) for the other eight objects, which have a < 2. There is no evidence that λ changes monotonically with spin-down age. The rate distribution itself is fitted reasonably well by an exponential for λ ⩾ 0.25 yr−1, with ⟨ λ ⟩ = 1.3+ 0.7−0.6 yr−1. For λ < 0.25 yr−1 the exact form is unknown; the exponential overestimates the number of glitching pulsars observed at low λ, where the limited total observation time exercises a selection bias. In order to reproduce the aggregate waiting-time distribution of the glitch population as a whole, the fraction of pulsars with λ > 0.25 yr−1 must exceed ~70%.

Subfields: Astronomy and Astrophysics, Atomic and Molecular Physics, and Optics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/70d81bd942caf3566192a805c0855fe002bc9448

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Citations in the corpus

Detection of 107 glitches in 36 southern pulsars (2012, background): “Melatos et al. (2008) showed that the waiting-time sequences of the glitches in seven pulsars followed a constant-rate Poisson process, which suggests that a neutron star could be a system fluctuating around a self-organised critical state.”
TIMING MEASUREMENTS OF THE RELATIVISTIC BINARY PULSAR PSR B1913+16 (2010, background): “The magnitude ∆f/f = 3.7× 10−11 of the event is smaller than almost all seen in the population of normal (not recycled) pulsars, with only some of the glitches in PSR B0355+54 having a comparably small magnitude (Melatos et al. 2008; Chukwude & Urama 2010).”
A study of 315 glitches in the rotation of 102 pulsars (2011, background): “Melatos et al. (2008) analysed the size and waiting time distributions of a number of pulsars and related their glitch activity to avalanche dynamics.”
45 years of rotation of the Crab pulsar (2014, background): “Melatos et al. (2008) include the Crab pulsar glitches in a comprehensive analysis of the statistics of the distributions of size and intervals between glitches, testing the hypothesis that these are determined by a random process of self-organised criticality.”
Gravitational Waves from Neutron Stars: A Review (2015, background): “Pulsar glitches are sudden jumps in the neutron star spin frequency with wide-ranging fractional amplitudes, 10−11 ν/ν 10−4 (Melatos et al. 2008; Espinoza et al. 2011; Espinoza et al. 2014).”