![]() Our results support the hypothesis that the MRI is able to generate magnetar-like large-scale magnetic fields. ![]() However, the buoyancy starts to strongly impact the MRI dynamo for Prandtl numbers close to unity.Ĭonclusions. ![]() Buoyancy due to the entropy gradient damps turbulence in the equatorial plane, but it has a relatively weak influence in the low Prandtl number regime overall, as expected from neutrino diffusion. By comparing these results with models without buoyancy or density stratification, we find that the key ingredient explaining the appearance of this mean-field behavior is the density gradient. Interestingly, an axisymmetric magnetic field at large scales is observed to oscillate with time, which can be described as a mean-field αΩ dynamo. The MRI generates a strong turbulent magnetic field and a nondominant equatorial dipole, which represents about 4.3% of the averaged magnetic field strength. This confirms most of our previous incompressible results when they are rescaled for density. We obtain a self-sustained turbulent MRI-driven dynamo. We performed a parameter study in which we investigated the influence of different approximations and the effect of the thermal diffusion through the Prandtl number. The thermodynamic background of the anelastic models was retrieved from the data of 1D core-collapse supernova simulations from the Garching group. Using the pseudo-spectral code MagIC, we performed 3D Boussinesq and anelastic magnetohydrodynamics simulations in spherical geometry with explicit diffusivities and with differential rotation forced at the outer boundary. The model focuses on the outer stratified region of the PNS that is stable to convection. We assess the impact of the density and entropy profiles on the MRI dynamo in a global model of a fast-rotating PNS. However, the impact of important physical ingredients, such as buoyancy and density stratification, on the efficiency of the MRI in generating a dipole field is still unknown.Īims. This scenario is supported by recent global incompressible models, which showed that a dipole field with magnetar-like intensity can be generated from small-scale turbulence. A promising mechanism for explaining magnetar formation is the amplification of the magnetic field by the magnetorotational instability (MRI) in fast-rotating protoneutron stars (PNS). In addition to fast rotation, these strong fields are also invoked to explain extreme stellar explosions, such as hypernovae, which are associated with long gamma-ray bursts and superluminous supernovae. Their magnetic dipole is constrained in the range of 10 14–10 15 G by the measurement of their spin-down. Magnetars are highly magnetized neutron stars that can produce a wide diversity of X-ray and soft gamma-ray emissions that are powered by magnetic dissipation. Université Paris Cité, Université Paris-Saclay, CNRS, CEA, Astrophysique, Instrumentation et Modélisation, 91191 Gif-sur-Yvette, FranceĬontext. Laboratoire AIM, CEA/DRF-CNRS-Université Paris Cité, IRFU/Département d’Astrophysique, CEA-Saclay 91191, FranceĮ-mail: Planck Institute for Gravitational Physics (Albert Einstein Institute), 14476 Potsdam, Germany Astronomical objects: linking to databasesĪ.Including author names using non-Roman alphabets.Suggested resources for more tips on language editing in the sciences Punctuation and style concerns regarding equations, figures, tables, and footnotes
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |