Pulsar glitches and vortex tangles: a neutron star super-mixture
Wed 1 August, 2018 @12:00 PM, level 7
Lisa Drummond, PhD Student
University of Melbourne
Pulsar glitches are a unique window into the dynamics of neutron matter at extreme densities. Modelling the physical mechanism that produces these glitches is an endeavour that spans many scales: from the quantum mechanical, microscopic interaction of vortices in the superfluid interior to the macroscopic motion of the rigid stellar crust. We can simulate vortex-avalanche-induced glitches by constructing a Gross-Pitaevskii model from first-principles, thereby incorporating the microscopic physics of superfluid vortices (Warszawski, Melatos, 2011; Melatos, Douglass & Simula, 2015). A complementary approach is to model pulsar glitches as a state-dependent Poisson process, thereby capturing the global behaviour of glitching pulsars (Fulgenzi, Melatos & Hughes, 2017). Bridging the stellar and microscopic scales described in these two approaches is an enormous computational and theoretical challenge. These models can each be extended in various ways, for example by including the interaction with the proton superconductor in the core (Drummond & Melatos, 2017). Competition between vortex-vortex repulsion and vortex-flux-tube attraction (pinning) leads to “glassy” behaviour characterized by multiple metastable states spaced closely in energy. Vortex tangles emerge as a consequence of the frustration in the system. The tangles evolve in a complicated fashion when driven out of equilibrium and a three-dimensional investigation reveals new vortex behaviours for misaligned magnetic and rotation axes.