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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

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.citation	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.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.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	journal article	es_ES
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.identifier.idgrec	049351	en
dc.type.hasVersion	VoR	es_ES
dc.identifier.url	http://www.aanda.org/index.php?option=article&access=doi&doi=10.1051/0004-6361/200811323	en