Mean-field dynamo action in protoneutron stars

Bonanno, A.; Rezzolla, Luciano; Урпин, В. А.

doi:10.1051/0004-6361:20031459

Cited by 66 publications

(96 citation statements)

References 24 publications

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“…The flexibility introduced by using the RungeKutta will allow us to consider not only more general Ohm laws and a variety of astrophysical dynamos [24,71], but also to use better dispersion relations as in [22], to calculate the velocities in the HLLE method and to describe more accurately also the nonrelativistic limit.…”

Section: Discussionmentioning

confidence: 99%

General-relativistic resistive magnetohydrodynamics in three dimensions: Formulation and tests

et al. 2013

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We present a new numerical implementation of the general-relativistic resistive magnetohydrodynamics (MHD) equations within the Whisky code. The numerical method adopted exploits the properties of implicitexplicit Runge-Kutta numerical schemes to treat the stiff terms that appear in the equations for large electrical conductivities. Using tests in one, two, and three dimensions, we show that our implementation is robust and recovers the ideal-MHD limit in regimes of very high conductivity. Moreover, the results illustrate that the code is capable of describing scenarios in a very wide range of conductivities. In addition to tests in flat spacetime, we report simulations of magnetized nonrotating relativistic stars, both in the Cowling approximation and in dynamical spacetimes. Finally, because of its astrophysical relevance and because it provides a severe testbed for general-relativistic codes with dynamical electromagnetic fields, we study the collapse of a nonrotating star to a black hole. We show that also in this case our results on the quasinormal mode frequencies of the excited electromagnetic fields in the Schwarzschild background agree with the perturbative studies within 0.7% and 5.6% for the real and the imaginary part of the ℓ = 1 mode eigenfrequency, respectively. Finally we provide an estimate of the electromagnetic efficiency of this process.

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Section: Discussionmentioning

confidence: 99%

General-relativistic resistive magnetohydrodynamics in three dimensions: Formulation and tests

et al. 2013

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“…In addition, a very complex field is expected from the formation process of magnetized neutron stars, since they are born hot, highly convective and differentially rotating [37,38]. During its early evolution, neutron star's magnetic fields can be significantly amplified and redistributed by several mechanisms including possibly dynamo action and shear instabilities.…”

Section: On the Isotropy Of The Pressurementioning

confidence: 99%

Properties of strongly magnetized ultradense matter and its effects on magnetar pulsations

2016

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We investigate the effect of strong magnetic fields on the adiabatic radial oscillations of hadronic stars. We describe magnetized hadronic matter within the framework of the relativistic nonlinear Walecka model and integrate the equations of relativistic radial oscillations to determine the fundamental pulsation mode. We consider that the magnetic field increases, in a density dependent way, from the surface, where it has a typical magnetar value of 10 15 G, to the interior of the star where it can be as large as 3 × 10 18 G. We show that magnetic fields of the order of 10 18 G at the stellar core produce a significant change in the frequency of neutron star pulsations with respect to unmagnetized objects. If radial pulsations are excited in magnetar flares, they can leave an imprint in the flare lightcurves and open a new window for the study of highly magnetized ultradense matter.

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“…In two complementary papers, Bonanno et al (2003) and Urpin & Gil (2004) recently presented studies on field generation in PNSs where the former deals with mean-field dynamos and the latter with small-scale ones.…”

Section: Introductionmentioning

confidence: 99%

“…In their strongly simplified model, Bonanno et al (2003) assume the mean e.m.f. to be constituted by isotropic α and β effects only and adopt purely radial dependences for differential rotation, the α-parameter and the turbulent magnetic diffusivity.…”

Section: Introductionmentioning

confidence: 99%

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The proto-neutron-star dynamo. Viability and impediments

Rheinhardt¹,

Geppert²

2005

A&A

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Abstract. We study convective motions taken from hydrodynamic simulations of rotating proto-neutron stars (PNSs) with respect to their ability to excite a dynamo instability which may be responsible for the giant neutron star magnetic fields. Since it is impossible to simulate the magnetic field evolution employing the actual magnetic Reynolds numbers (Rm) resulting from the hydrodynamic simulations, (smallest) critical Rms and the corresponding field geometries are derived on the kinematic level by rescaling the velocity amplitudes. It turns out that the actual values of Rm are by many orders of magnitude larger than the critical values found. A dynamo might therefore start to act vigorously very soon after the onset of convection. But as in general dynamo growth rates are non-monotonous functions of Rm the later fate of the magnetic field is uncertain. Hence, no reliable statements on the existence and efficiency of PNS dynamos can be drawn without considering the interplay of magnetic field and convection from the beginning. Likewise, in so far as convection inside the PNS is regarded to be essential in re-launching the supernova explosion, a revision of its role in this respect could turn out to be necessary.

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Mean-field dynamo action in protoneutron stars

Cited by 66 publications

References 24 publications

General-relativistic resistive magnetohydrodynamics in three dimensions: Formulation and tests

General-relativistic resistive magnetohydrodynamics in three dimensions: Formulation and tests

Properties of strongly magnetized ultradense matter and its effects on magnetar pulsations

The proto-neutron-star dynamo. Viability and impediments

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