Axisymmetric and stationary structures of magnetized barotropic stars with extremely strong magnetic fields deep inside

Fujisawa, Kotaro; Yoshida, Shin’ichirou; Eriguchi, Yoshiharu

doi:10.1111/j.1365-2966.2012.20614.x

Cited by 47 publications

(70 citation statements)

References 61 publications

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“…Furthermore, this ratio seems to be bounded by a certain maximum value as seen in Figure 3 (left panel), above which the ratio would decrease, as already pointed out in the literature (Lander & Jones 2009, Ciolfi et al 2009, Fujisawa et al 2012), although such a behavior for large s and density profile considered here is not reached in our calculations. It is interesting to see, however, that we do reach a maximum in the ratio of toroidal to poloidal flux (Figure 3, right panel).…”

Section: Numerical Solutions and Discussionmentioning

confidence: 45%

“…Several authors (Lander & Jones 2009;Ciolfi et al 2009;Fujisawa et al 2012;Gourgouliatos et al 2013) have explored the possible axially symmetric equilibria in barotropic stars, generally finding that the fraction of the total magnetic energy corresponding to the toroidal component, E tor /E mag , is at most a few %. In addition to not being enough to account for the energy emitted by magnetars, this would be insufficient to stabilize the poloidal component (Braithwaite 2009;Akgün et al 2013), as confirmed by the simulations of Lander & Jones (2012).…”

Section: Overviewmentioning

confidence: 99%

“…In this context, barotropic equations of state, where pressure is a function solely of density, are often assumed to describe the matter within these objects (Yoshida & Eriguchi 2006;Haskell et al 2008;Lander & Jones 2009;Ciolfi et al 2009;Fujisawa et al 2012). Barotropy strongly restricts the range of possible equilibrium configurations and does not strictly represent the realistic stably stratified matter within these objects, which is likely to be an essential ingredient in the stability of magnetic fields in stars on short timescales (Reisenegger 2009).…”

Section: Overviewmentioning

confidence: 99%

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Magnetohydrodynamic equilibria in barotropic stars

Armaza¹,

Reisenegger²,

Valdivia

et al. 2013

Proc. IAU

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Abstract. Although barotropic matter does not constitute a realistic model for magnetic stars on short timescales, it would be interesting to confirm a recent conjecture that states that magnetized stars with a barotropic equation of state would be dynamically unstable (Reisenegger 2009). In this work we construct a set of barotropic equilibria, which can eventually be tested using a stability criterion. A general description of the ideal MHD equations governing these equilibria is summarized, allowing for both poloidal and toroidal magnetic field components. A new finite-difference numerical code is developed in order to solve the so-called Grad-Shafranov equation describing the equilibrium of these configurations, and some properties of the equilibria obtained are briefly discussed.

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Section: Numerical Solutions and Discussionmentioning

confidence: 45%

Section: Overviewmentioning

confidence: 99%

Section: Overviewmentioning

confidence: 99%

See 1 more Smart Citation

Magnetohydrodynamic equilibria in barotropic stars

Armaza¹,

Reisenegger²,

Valdivia

et al. 2013

Proc. IAU

View full text Add to dashboard Cite

show abstract

“…Particular efforts have been recently aimed at investigating the stability of various magnetic configurations. However due to the complexity of the problem, models have been worked either in Newtonian regime [15,16,17], or in GR with a perturbative approach [18,19,20], and with currents purely confined to the interior. Only recently [21,22] they have been worked out in the fully non-linear GR regime, including the possibility of currents extending outside into a magnetosphere [23].…”

Section: Introductionmentioning

confidence: 99%

Modeling the structure of magnetic fields in Neutron Stars: from the interior to the magnetosphere

Bucciantini

Pili

Zanna

2016

J. Phys.: Conf. Ser.

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Abstract. The phenomenology of the emission of pulsars and magnetars depends dramatically on the structure and properties of their magnetic field. In particular it is believed that the outbursting and flaring activity observed in AXPs and SRGs is strongly related to their internal magnetic field. Recent observations have moreover shown that charges are present in their magnetospheres supporting the idea that their magnetic field is tightly twisted in the vicinity of the star. In principle these objects offer a unique opportunity to investigate physics in a regime beyond what can be obtained in the laboratory. We will discuss the properties of equilibrium models of magnetized neutron stars, and we will show how internal and external currents can be related. These magnetic field configurations will be discussed considering also their stability, relevant for their origin and possibly connected to events like SNe and GRBs. We will also show what kind of deformations they induce in the star, that could lead to emission of gravitational waves. In the case of a twisted magnetosphere we will show how the amount of twist regulates their general topology. A general formalism based on the simultaneous numerical solution of the general relativistic Grad-Shafranov equation and Einstein equations will be presented.

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“…Where F is also a conserved quantity (F ≡ F (Ψ)) which is related to the Lorentz force (see Fujisawa et al 2012). If the outside of the star is vacuum, I must vanish in the region.…”

Section: Formulation and Arbitrary Functionsmentioning

confidence: 99%

Magnetic field structures inside magnetars with strong toroidal field

Fujisawa

2013

Proc. IAU

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Abstract. We have analyzed the magnetized equilibrium studies with strong toroidal magnetic fields and found that the negative toroidal current density inside the star is very important for the strong toroidal magnetic fields. The strong toroidal magnetic fields require the strong poloidal current, but the strong poloidal current results in the localized strong toroidal current density in the axisymmetric system. This localized toroidal current changes the magnetic field configuration and makes the size of the toroidal magnetic field region smaller. As a result, the toroidal magnetic field energy can not become large. We need to cancel out the localized toroidal current density in order to obtain the large toroidal fields solutions. We have found and showed that the negative toroidal current cancels out the localized toroidal current density and sustain the large toroidal magnetic field energy inside the star. We can explain the magnetized equilibrium studies with strong toroidal magnetic fields systematically using the negative current density. Physical meaning of the negative current is key to the magnetar interior magnetic fields.

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Axisymmetric and stationary structures of magnetized barotropic stars with extremely strong magnetic fields deep inside

Cited by 47 publications

References 61 publications

Magnetohydrodynamic equilibria in barotropic stars

Magnetohydrodynamic equilibria in barotropic stars

Modeling the structure of magnetic fields in Neutron Stars: from the interior to the magnetosphere

Magnetic field structures inside magnetars with strong toroidal field

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