On the structure of envelopes of rapidly rotating neutron stars

Geppert, U.; Wiebicke, H.J.

doi:10.1016/0273-1177(88)90482-6

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…Above, τ = ω B τ/B, and I (2) , I (3) are expressions that contain the Clebsch-Gordan coefficients which reflect the coupling properties of the field modes with different multipolarity (see Eq. ( 60) in Geppert & Wiebicke (1991)).…”

Section: Basic Equations and Formalismmentioning

confidence: 98%

“…Hereafter, we follow the notation of Geppert & Wiebicke (1991). The two components are described by two functions, Φ(r, θ, ϕ, t)…”

Section: Basic Equations and Formalismmentioning

confidence: 99%

“…In this paper we will restrict ourselves to axially symmetric field configurations, i.e., the index m = 0 and we will drop it henceforth. Following the derivation of Geppert & Wiebicke (1991) the nonlinear coupling terms are…”

Section: Basic Equations and Formalismmentioning

confidence: 99%

“…Hereafter, we follow the notation of Geppert & Wiebicke (1991). The two components are described by two functions, Φ(r, θ, ϕ, t) and Ψ(r, θ, ϕ, t), where r, θ, and ϕ are the usual spherical coordinates.…”

Section: Basic Equations and Formalismmentioning

confidence: 99%

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Magnetic field dissipation in neutron star crusts: from magnetars to isolated neutron stars

Pons¹,

Geppert²

2007

A&A

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Context. We study the non-linear evolution of magnetic fields in neutron star crusts with special attention to the influence of the Hall drift. Aims. Our goal is to understand the conditions for fast dissipation due to the Hall term in the induction equation. We study the interplay of Ohmic dissipation and Hall drift in order to find a timescale for the overall crustal field decay. Methods. We solve numerically the Hall induction equation by means of a hybrid method (spectral in angles but finite differences in the radial coordinate). The microphysical input consists of the most modern available crustal equation of state, composition and electrical conductivities.Results. We present the first long term simulations of the non-linear magnetic field evolution in realistic neutron star crusts with a stratified electron number density and temperature dependent conductivity. We show that Hall drift influenced Ohmic dissipation takes place in neutron star crusts on a timescale of 10 6 years. When the initial magnetic field has magnetar strength, the fast Hall drift results in an initial rapid dissipation stage that lasts ∼ 10 4 years. The interplay of the Hall drift with the temporal variation and spatial gradient of conductivity tends to favor the displacement of toroidal fields toward the inner crust, where stable configurations can last for ∼ 10 6 years. We show that the thermally emitting isolated neutron stars, as the Magnificent Seven, are very likely descendants of neutron stars born as magnetars.

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Section: Basic Equations and Formalismmentioning

confidence: 98%

“…Hereafter, we follow the notation of Geppert & Wiebicke (1991). The two components are described by two functions, Φ(r, θ, ϕ, t)…”

Section: Basic Equations and Formalismmentioning

confidence: 99%

Section: Basic Equations and Formalismmentioning

confidence: 99%

Section: Basic Equations and Formalismmentioning

confidence: 99%

See 2 more Smart Citations

Magnetic field dissipation in neutron star crusts: from magnetars to isolated neutron stars

Pons¹,

Geppert²

2007

A&A

Self Cite

201

253

View full text Add to dashboard Cite

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“…These gradients are especially strong in the radial direction where they can exceed ∼ 10 8 Kcm −1 . Across the rim of the polar cap the meridional temperature gradients of ∼ 10 4 Kcm −1 may drive a thermoelectric instability which causes the generation of an azimuthal magnetic field along that rim (Blandford et al 1983;Urpin et al 1986;Geppert & Wiebicke 1995). In the context of emission mode changing the thermal drift of the magnetic field by these temperature gradients are of special interest.…”

Section: Basic Equationsmentioning

confidence: 99%

Rapid Modification of Neutron Star Surface Magnetic Field: A proposed mechanism for explaining Radio Emission State Changes in Pulsars

Geppert,

Basu,

Mitra

et al. 2021

Preprint

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The radio emission in many pulsars show sudden changes, usually within a period, that cannot be related to the steady state processes within the inner acceleration region (IAR) above the polar cap. These changes are often quasi-periodic in nature, where regular transitions between two or more stable emission states are seen. The durations of these states show a wide variety ranging from several seconds to hours at a time. There are strong, small scale magnetic field structures and huge temperature gradients present at the polar cap surface. We have considered several processes that can cause temporal modifications of the local magnetic field structure and strength at the surface of the polar cap. Using different magnetic field strengths and scales, and also assuming realistic scales of the temperature gradients, the evolutionary timescales of different phenomena affecting the surface magnetic field was estimated. We find that the Hall drift results in faster changes in comparison to both Ohmic decay and thermoelectric effects. A mechanism based on the Partially Screened Gap (PSG) model of the IAR has been proposed, where the Hall and thermoelectric oscillations perturb the polar cap magnetic field to alter the sparking process in the PSG. This is likely to affect the observed radio emission resulting in the observed state changes.

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Magneto–Thermal Evolution of Neutron Stars with Emphasis to Radio Pulsars

Geppert¹

2017

J Astrophys Astron

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The magnetic and thermal evolution of neutron stars is a very complex process with many, also non-linear, interactions. For a decent understanding of neutron star physics, these evolutions cannot be considered isolated. A brief overview is presented, which describes the main magneto -thermal interactions that determine the fate both of isolated neutron stars and accreting ones. Special attention is devoted to the interplay of thermal and magnetic evolution at the polar cap of radio pulsars. There, a strong meridional temperature gradient is maintained over the lifetime of radio pulsars. It may be strong enough to drive thermoelectric magnetic field creation which perpetuate a toroidal magnetic field around the polar cap rim. Such a local field component may amplify and curve the poloidal surface field at the cap, forming a strong and small scale magnetic field there as required for the radio emission of pulsars.Key words: stars: neutron -stars: magnetic fields -pulsars: general -stars: interiors PREFACEWhen I started to try to understand some aspects of neutron star physics, one of the first papers I read was Srinivasan & van den Heuvel (1982) about the evolution of millisecond pulsars. Then the connection between the (at that time in optical light) invisible pulsars and the fascinating manifestations of supernova remnants (Srinivasan et al. 1984) increased my interest in this branch of astrophysics. The observation of millisecond pulsars in the early eighties was a challenge, which was met by Prof. Srinivasan and his colleagues (see e.g. Bhattacharya & Srinivasan (1986);Srinivasan (1989)). Later the pioneering work of Srinivasan et al. (1990) triggered my interest to understand how the very long-lived core magnetic field is affected by the rotational history of neutron stars and how the evolutions of core and crustal field are coupled to each other. Meanwhile Prof. Srinivasan enriched our knowledge about neutron stars by many contributions, among others about their evolution in accreting binary systems, about the recycling of old pulsars to millisecond pulsars, about the supernova remnants and pulsar wind nebulae which are results of neutron star births, about the use of radiotelescope for pulsar observations and about many other topics. As far as I can see being a far distant observer, Prof. Srinivasan succeeded also in the formation of a group of excellent and worldwide renown Indian scientists working in the field of neutron star physics.⋆ E-mail:ulrich.geppert@dlr.deMay be there exists a not yet discovered age-relativistic effect that makes the time running faster when seen by an aging person. It seems to be this effect that made me surprised to recognize that Prof. Srinivasan celebrates already his 75th birthday. This special issue is a good opportunity to esteem his life-work and I am happy that I can contribute to it. THE MANY FACETS OF MAGNETO -THERMAL INTERACTIONS

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On the structure of envelopes of rapidly rotating neutron stars

Cited by 4 publications

References 3 publications

Magnetic field dissipation in neutron star crusts: from magnetars to isolated neutron stars

Magnetic field dissipation in neutron star crusts: from magnetars to isolated neutron stars

Rapid Modification of Neutron Star Surface Magnetic Field: A proposed mechanism for explaining Radio Emission State Changes in Pulsars

Magneto–Thermal Evolution of Neutron Stars with Emphasis to Radio Pulsars

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