Semi-global simulations of the magneto-rotational instability in core collapse supernovae
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Semi-global simulations of the magneto-rotational instability in core collapse supernovae

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Semi-global simulations of the magneto-rotational instability in core collapse supernovae

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dc.contributor.author Aloy Toras, Miguel Angel
dc.contributor.author Obergaulinger, M.
dc.contributor.author Cerdá Durán, Pablo
dc.contributor.author Müller, E.
dc.date.accessioned 2010-07-28T11:57:52Z
dc.date.available 2010-07-28T11:57:52Z
dc.date.issued 2009
dc.identifier.uri http://hdl.handle.net/10550/16711
dc.description.abstract Context. Possible effects of magnetic fields in core collapse supernovae rely on an efficient amplification of the weak pre-collapse fields. It has been suggested that the magneto-rotational instability (MRI) leads to a rapid growth for these weak seed fields. Although plenty of MRI studies exist for accretion disks, the application of their results to core collapse supernovae is inhibited as the physics of supernova cores is substantially different from that of accretion discs. Aims. We address the problem of growth and saturation of the MRI in core collapse supernovae by studying its evolution by means of semi-global simulations, which combine elements of global and local simulations by taking the presence of global background gradients into account and using a local computational grid. We investigate, in particular, the termination of the growth of the MRI and the properties of the turbulence in the saturated state. Methods. We analyze the dispersion relation of the MRI to identify different regimes of the instability. This analysis is complemented by semi-global ideal MHD simulations, where we consider core matter in a local computational box (size ∼1 km) rotating at sub- Keplerian velocity and where we allow for the presence of a radial entropy gradient, but neglect neutrino radiation. Results. We identify six regimes of the MRI depending on the ratio of the entropy and angular velocity gradient. Our numerical models confirm the instability criteria and growth rates for all regimes relevant to core-collapse supernovae. The MRI grows exponentially on time scales of milliseconds, the flow and magnetic field geometries being dominated by channel flows. We find MHD turbulence and efficient transport of angular momentum. The MRI growth ceases once the channels are disrupted by resistive instabilities (stemming from to the finite conductivity of the numerical code), and MHD turbulence sets in. From an analysis of the growth rates of the resistive instabilities, we deduce scaling laws for the termination amplitude of the MRI, which agree well with our numerical models. We determine the dependence of the development of large-scale coherent flow structures in the saturated state on the aspect ratio of the simulation boxes. Conclusions. The MRI can grow rapidly under the conditions considered here, i.e., a rapidly rotating core in hydrostatic equilibrium, possibly endowed with a nonvanishing entropy gradient, leading to fields exceeding 1015 G. More investigations are required to cover the parameter space more comprehensively and to include more physical effects. en
dc.language.iso en en
dc.relation http://www.aanda.org/index.php?option=article&access=doi&doi=10.1051/0004-6361/200811323 en
dc.source OBERGAULINGER, M., CERDÁ-DURÁN, P., MÜLLER, E. and ALOY, M. A. (2009): Semi-global simulations of the magneto-rotational instability in core collapse supernovae, Astronomy and Astrology, núm. 498, vol 1, pp. 241 en
dc.subject Magnetohydrodynamics (MHD); Instabilities; Stars : supernovae : general; Stars : magnetic fields en
dc.title Semi-global simulations of the magneto-rotational instability in core collapse supernovae en
dc.type info:eu-repo/semantics/article en
dc.type info:eu-repo/semantics/publishedVersion en
dc.subject.unesco UNESCO::ASTRONOMÍA Y ASTROFÍSICA::Cosmología y cosmogonia::Estrellas en
dc.subject.unesco UNESCO::ASTRONOMÍA Y ASTROFÍSICA::Cosmología y cosmogonia::Otras en
dc.identifier.doi 10.1051/0004-6361/200811323 en
dc.description.private aloy@uv.es en
dc.identifier.idgrec 049351 en

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