From the dynamics of a hydraulic jump to the the asymmetric character of stellar explosions

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• Thierry Foglizzo (Service d’Astrophysique, CEA Saclay)
• Monday 21 November 2016, 16:00-17:00
• MR14, Centre for Mathematical Sciences, Wilberforce Road, Cambridge.

If you have a question about this talk, please contact Jean Teyssandier.

The explosion mechanism of massive stars is a challenging problem where multidimensional instabilities seem to play a central role. Non axisymmetric instabilities such as the Standing Accretion Shock Instability and neutrino-driven convection are able to break the spherical symmetry and impact the birth condition of pulsars. Surprisingly, the SASI instability can be illustrated with a simple experiment based on a shallow water analogy. The SWASI fountain involves a circular hydraulic jump in a radial converging flow, which becomes oscillatory and turns into a self sustained rotating pattern. Numerical simulations and a perturbative analysis suggest that this unstable dynamics is due to the interaction of vorticity and surface gravity waves. The most recent experimental setup uses the global rotation of the fountain to study the redistribution of angular momentum in the collapsing stellar core. A new m=1 spiral mode reminiscent of the Papaloizou-Pringle instability, fed by differential rotation, has been characterized experimentally using surface PIV . Results are discussed in view of the constraints set by stellar evolution and by the spin properties of pulsars.

This talk is part of the DAMTP Astrophysics Seminars series.

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