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We have succeeded in obtaining magnetized equilibrium states with differential rotation and differential toroidal magnetic fields. If an internal toroidal field of a proto-neutron star is wound up from the initial poloidal magnetic field by…

High Energy Astrophysical Phenomena · Physics 2015-08-28 Kotaro Fujisawa

In previous work stable approximately axisymmetric equilibrium configurations for magnetic stars were found by numerical simulation. Here I investigate the conditions under which more complex, non-axisymmetric configurations can form. I…

Astrophysics · Physics 2009-11-13 J. Braithwaite

We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal magnetic field configurations to study the behavior of the Tayler instability. For the first time the simultaneous action of rotation and magnetic diffusion are…

Solar and Stellar Astrophysics · Physics 2015-05-27 Juan C. Ibañez-Mejia , Jonathan Braithwaite

We examine the MHD instabilities arising in the radiation zone of a differentially rotating star, in which a poloidal field of fossil origin is sheared into a toroidal field. We focus on the non-axisymmetric instability that affects the…

Astrophysics · Physics 2009-11-13 J. -P. Zahn , A. S. Brun , S. Mathis

Context. The understanding of fossil fields origin, topology and stability is one of the corner stones of the stellar magnetism theory. On one hand, since they survive over secular time-scales, they may modify the structure and the…

Solar and Stellar Astrophysics · Physics 2010-03-16 V. Duez , S. Mathis

We have studied numerically the evolution of magnetic fields in barotropic neutron stars, by performing nonlinear magnetohydrodynamical simulations with the code PLUTO. For both initially predominantly poloidal and toroidal fields, with…

High Energy Astrophysical Phenomena · Physics 2020-09-22 Ankan Sur , Brynmor Haskell , Emily Kuhn

Neutron stars can harbor extremely strong magnetic fields, yet the structure and stability of their magnetic field configuration remain poorly understood. Observations of pulsars indicate that the large-scale external field is predominantly…

High Energy Astrophysical Phenomena · Physics 2026-05-25 Aurora Capobianco , William Cook , Sebastiano Bernuzzi , Brynmor Haskell , Jacob Fields

We present numerical solutions for stationary and axisymmetric equilibriums of compact stars associated with extremely strong magnetic fields. The interior of the compact stars is assumed to satisfy ideal magnetohydrodynamic (MHD)…

General Relativity and Quantum Cosmology · Physics 2025-12-22 Koji Uryu , Shijun Yoshida , Eric Gourgoulhon , Charalampos Markakis , Kotaro Fujisawa , Antonios Tsokaros , Keisuke Taniguchi , Mina Zamani

We derive general equations for axisymmetric Newtonian MHD and use these as the basis of a code for calculating equilibrium configurations of rotating magnetised neutron stars in a stationary state. We investigate the field configurations…

Solar and Stellar Astrophysics · Physics 2012-02-10 S. K. Lander , D. I. Jones

As another step towards understanding the long-term evolution of the magnetic field in neutron stars, we provide the first simulations of ambipolar diffusion in a spherical star. Restricting ourselves to axial symmetry, we consider a…

High Energy Astrophysical Phenomena · Physics 2017-07-17 F. Castillo , A. Reisenegger , J. A. Valdivia

We develop the formalism for computing the magnetic field within an axisymmetric neutron star with a strong Type II superconductor core surrounded by a normal conductor. The formalism takes full account of the constraints imposed by…

High Energy Astrophysical Phenomena · Physics 2014-09-30 K. T. Henriksson , I. Wasserman

Stationary and axisymmetric solutions of relativistic rotating stars with strong mixed poloidal and toroidal magnetic fields are obtained numerically. Because of the mixed components of the magnetic field, the underlying stationary and…

High Energy Astrophysical Phenomena · Physics 2014-11-13 Koji Uryu , Eric Gourgoulhon , Charalampos Markakis , Kotaro Fujisawa , Antonios Tsokaros , Yoshiharu Eriguchi

We find general relativistic solutions of equilibrium magnetic field configurations in magnetars, extending previous results of Colaiuda et al. (2008). Our method is based on the solution of the relativistic Grad-Shafranov equation, to…

Solar and Stellar Astrophysics · Physics 2010-11-02 R. Ciolfi , V. Ferrari , L. Gualtieri , J. A. Pons

The question of the origin and evolution of magnetic fields in stars possessing a radiative envelope, like the A-type stars, is still regarded as a challenge for stellar physics. Those zones are likely to be differentially rotating, which…

Solar and Stellar Astrophysics · Physics 2015-06-23 Laurène Jouve , Thomas Gastine , François Lignières

We have analyzed magnetized equilibrium states and showed a condition for appearance of the prolate and the toroidal magnetic field dominated stars by analytic approaches. Both observations and numerical stability analysis support that the…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Kotaro Fujisawa , Yoshiharu Eriguchi

We have succeeded in obtaining magnetized star models that have extremely strong magnetic fields in the interior of the star. In our formulation, arbitrary functions of the magnetic flux function appear in the expression for the current…

High Energy Astrophysical Phenomena · Physics 2013-04-03 Kotaro Fujisawa , Shin'ichirou Yoshida , Yoshiharu Eriguchi

The equilibrium of a resistive axisymmetric plasma with purely toroidal flow surrounded by a conductor is investigated within the framework of the nonlinear magnetohydrodynamic theory. It is proved that a) the poloidal current density…

Plasma Physics · Physics 2009-10-30 G. N. Throumoulopoulos

We present Hall equilibrium solutions for neutron stars crusts containing toroidal and poloidal magnetic field. Some simple cases are solved analytically while more complicated configurations are found numerically through a Gauss-Seidel…

Solar and Stellar Astrophysics · Physics 2013-05-02 K. N. Gourgouliatos , A. Cumming , M. Lyutikov , A. Reisenegger

We calculate non-axisymmetric oscillations of neutron stars magnetized by purely poloidal magnetic fields. We use polytropes of index $n=1$ and 1.5 as a background model, where we ignore the equilibrium deformation due to the magnetic…

High Energy Astrophysical Phenomena · Physics 2015-12-16 Hidetaka Asai , Umin Lee , Shijun Yoshida

The stability of large-scale magnetic fields in rotating stars is explored, using 3D numerical hydrodynamics to follow the evolution of an initial poloidal field. It is found that the field is subject to an instability, located initially on…

Astrophysics · Physics 2009-11-13 J. Braithwaite