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

By M. Obergaulinger, P. Cerdá-Durán, E. Müller, M. Aloy. 2008

134 citations recorded by the source corpus.

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 $10^{15}~\mathrm{G}$. More investigations are required to cover the parameter space more comprehensively and to include more physical effects.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/155bb422e605f015b07ac7917c8db0c6540bf317

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Citations in the corpus

MAGNETOROTATIONAL CORE-COLLAPSE SUPERNOVAE IN THREE DIMENSIONS (2014, background): “The magnetorotational instability (MRI, Balbus & Hawley 1991; Akiyama et al. 2003; Obergaulinger et al. 2009) is one possibility.”
r-process Nucleosynthesis from Three-dimensional Magnetorotational Core-collapse Supernovae (2017, background): “…by flux-compression from a highly magnetized progenitor core or via amplification by the magnetorotational instability (MRI, Balbus & Hawley 1991; Akiyama et al. 2003; Obergaulinger et al. 2009) and dynamo action (Mösta et al. 2015) in the early postbounce evolution of the protoneutron star.”
MAGNETOROTATIONALLY DRIVEN SUPERNOVAE AS THE ORIGIN OF EARLY GALAXY r-PROCESS ELEMENTS? (2012, background): “This motivates our choice of the high initial poloidal field strength, which by flux compression and rotational winding leads to magnetic fields whose magnitude roughly agree with those expected from the magnetorotational instability at saturation (Obergaulinger et al. 2009).”
THE r-PROCESS NUCLEOSYNTHESIS IN THE VARIOUS JET-LIKE EXPLOSIONS OF MAGNETOROTATIONAL CORE-COLLAPSE SUPERNOVAE (2015, background): “The role of MRI during core-collapse has been studied, focusing on several aspects (Akiyama et al. 2003; Obergaulinger et al. 2009; Masada et al. 2012; Obergaulinger et al. 2014; Masada et al. 2015).”
Multiple physical elements to determine the gravitational-wave signatures of core-collapse supernovae (2011, background): “…in global simulations, MHD outflows might be produced even for more weakly magnetized cores because the MRI can exponentially amplify the initial magnetic fields to a dynamically important strength within several rotational periods (e.g., colle tive references in Obergaulinger et al. (2009) [171]).”
THE MISSING LINK: MERGING NEUTRON STARS NATURALLY PRODUCE JET-LIKE STRUCTURES AND CAN POWER SHORT GAMMA-RAY BURSTS (2011, background): “…from trivial and a nonlinear dynamo may explain why the MRI brings a magnetic field self-organization, as it has been also suggested in case of MRI-mediated growth of the magnetic field in the conditions met in the collapse of massive stellar cores (Lesur & Ogilvie 2008; Obergaulinger et al. 2009).”
The Intermediate r-process in Core-collapse Supernovae Driven by the Magneto-rotational Instability (2016, background): “The MRI in proto-NS cores has been investigated on several scales (with related limitations) from local boxes (Obergaulinger et al. 2009; Masada et al. 2012; Rembiasz et al. 2016) to global scales (Sawai et al. 2013; Mösta et al. 2015).”
Neutron Star Mergers Might Not Be the Only Source of r-process Elements in the Milky Way (2018, background): “In addition, there are small scale turbulences and instabilities such as the magneto-rotational instability (e.g., Obergaulinger et al. 2009) that can amplify the magnetic field.”