Time-dependent Force-free Pulsar Magnetospheres: Axisymmetric and Oblique Rotators

Spitkovsky, Anatoly

doi:10.1086/507518

Cited by 825 publications

(963 citation statements)

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“…Changes in the magnetospheric currents concur with changes in the braking torque on the star, as evidenced in correlated variations in the radio pulses and inṖ [161]. The spin-down rate is indeed larger by a factor 3 2 (1 + sin 2 αB)/ sin 2 αB for a force-free magnetosphere than for a vacuum dipole [14,59], so changes in the charge supply can impact the rotation, even if a dense plasma remains trapped in the closed-field region [134]. Mode switching, on the other hand, suggests current reorganizations from some open field lines to others, or the shutting off of specific components in composite, multi-beam light curves.…”

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confidence: 65%

“…[132]. The time-dependent solution for the oblique magnetosphere (Figure 2) appeared in 2006 [14]. These simulations solve the time-dependent Maxwell's Equations, in the limit of inertiafree plasma and under the imposed condition that E · B = 0, with a current along each field line that is adjusted to sustain the force-free electric field.…”

Section: Mhd Magnetosphere Modelsmentioning

confidence: 99%

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Gamma-ray pulsars: A gold mine

Grenier

Harding

2015

Comptes Rendus. Physique

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The most energetic neutron stars, powered by their rotation, are capable of producing pulsed radiation from the radio up to γ rays with nearly TeV energies. These pulsars are part of the universe of energetic and powerful particle accelerators, using their uniquely fast rotation and formidable magnetic fields to accelerate particles to ultra-relativistic speed. The extreme properties of these stars provide an excellent testing ground, beyond Earth experience, for nuclear, gravitational, and quantum-electrodynamical physics. A wealth of γ-ray pulsars has recently been discovered with the Fermi Gamma-Ray Space Telescope. The energetic γ rays enable us to probe the magnetospheres of neutron stars and particle acceleration in this exotic environment. We review the latest developments in this field, beginning with a brief overview of the properties and mysteries of rotation-powered pulsars, and then discussing γ-ray observations and magnetospheric models in more detail. RésuméLes pulsars γ : une mine d'or : Lesétoilesà neutrons les plus puissantes, qui tirent leurénergie de leur rotation, sont capables d'émettre des impulsions lumineuses des ondes radio jusqu'aux rayons γ d'énergies proches du TeV. Ces pulsars font partie des puissants accélérateurs de particules de l'Univers, profitant de leur rotation unique et de leur formidable champ magnétique pour accélérer des particules jusqu'à des vitesses ultra-relativistes. Les propriétés extrêmes de cesétoiles permettent de tester la physique nucléaire, la gravitation et l'électrodynamique quantique dans des conditions inaccessibles sur Terre. Le télescope gamma spatial Fermi vient de révéler un richeéchantillon de pulsars γ. Leur rayonnement γénergétique permet de sonder la magnétosphère desétoilesà neutrons et d'étudier l'accélération de particules dans cet environnement exotique. Nous présentons les derniers développements de ce domaine, en commençant par une rapide revue des propriétés et mystères soulevés par ces pulsars, puis en détaillant plus avant les observations γ et les modèles magnétosphériques.Keywords : pulsar ; neutron star ; magnetosphere ; gamma rays ; acceleration Mots-clés : pulsar ;étoileà neutrons ; magnétosphère ; rayons gamma ; accélération Neutron stars, pulsars, and their puzzlesA neutron star is an extreme object in many regards. It is a compact, rapidly spinning, highly magnetized star, formed from the core of a massive star which runs out of nuclear power and collapses under its own gravity, with 53 radio-loud and γ-loud young pulsars (orange upward triangles), 37 radio-faint and γ-loud young pulsars (red downward triangles), 71 radio-loud and γ-loud millisecond pulsars (green filled circles, circled in black and red when in black-widow and redback systems, respectively), and 2256 other radio pulsars (light blue). Recently discovered millisecond pulsars, with noṖ measurement yet, are plotted as squares atṖ near 10 −21 . Lines of constant spin-down power (brown) and polar magnetic field strength (green) are given for a magnetic dipole i...

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mentioning

confidence: 65%

Section: Mhd Magnetosphere Modelsmentioning

confidence: 99%

Gamma-ray pulsars: A gold mine

Grenier

Harding

2015

Comptes Rendus. Physique

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“…According to Beskin, Gurevich, & Istomin (1993);Spitkovsky (2006) ;Tchekhovskoy, Philippov, & Spitkovsky (2016), the spin-down power associated with magnetic field, E mag rot , can be estimated as…”

Section: Narrow Low-temperature Stability Peaks [Model (A)]mentioning

confidence: 99%

R modes and neutron star recycling scenario

Chugunov¹,

Gusakov²,

Kantor

2017

Monthly Notices of the Royal Astronomical Society

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To put new constraints on the r-mode instability window, we analyse the formation of millisecond pulsars (MSPs) within the recycling scenario, making use of three sets of observations: (a) X-ray observations of neutron stars (NSs) in low-mass X-ray binaries; (b) timing of millisecond pulsars; and (c) X-ray and UV observations of MSPs. As shown in previous works, r-mode dissipation by shear viscosity is not sufficient to explain observational set (a), and enhanced r-mode dissipation at the red-shifted internal temperatures T ∞ ∼ 10 8 K is required to stabilize the observed NSs. Here, we argue that models with enhanced bulk viscosity can hardly lead to a self-consistent explanation of observational set (a) due to strong neutrino emission, which is typical for these models (unrealistically powerful energy source is required to keep NSs at the observed temperatures). We also demonstrate that the observational set (b) , combined with the theory of internal heating and NS cooling, provides evidence of enhanced r-mode dissipation at low temperatures, T ∞ ∼ 2×10 7 K. Observational set (c) allows us to set an upper limit on the internal temperatures of MSPs, T ∞ < 2 × 10 7 K (assuming a canonical NS with the accreted crust). Recycling scenario can produce MSPs at these temperatures only if r-mode instability is suppressed in the whole MSP spin frequency range (ν 750 Hz) at temperatures 2 × 10 7 T ∞ 3 × 10 7 K, providing thus a new constraint on the r-mode instability window. These observational constraints are analysed in more details in application to the resonance uplift scenario of Gusakov et al. (2014b,a).

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“…As recalled by Perera et al (2014), in general, pulsar magnetosphere models are constructed at the following two limits: (a) a vacuum limit (Deutsch 1955); and (b) a force-free magnetohydrodynamics (MHD) limit with a plasma-filled magnetosphere (Spitkovsky 2006). However, a true magnetosphere operates between these two limits.…”

Section: Introductionmentioning

confidence: 99%

General solution for the vacuum electromagnetic field in the surroundings of a rotating star

Bonazzola¹,

Mottez²,

Heyvaerts³

2014

A&A

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Aims. Many recent observations of pulsars and magnetars can be interpreted in terms of neutron stars with multipole electromagnetic fields. As a first approximation, we investigate the multipole magnetic and electric fields in the environment of a rotating star when this environment is deprived of plasma. Methods. We compute a multipole expansion of the electromagnetic field in vacuum for a given magnetic field on the conducting surface of the rotating star. Then, we consider a few consequences of multipole fields of pulsars. Results. We provide an explicit form of the solution. For each spherical harmonic of the magnetic field, the expansion contains a finite number of terms. A multipole magnetic field can provide an explanation for the stable sub-structures of pulses, and they offer a solution to the problem of current closure in pulsar magnetospheres. Conclusions. This computation generalises the widely used model of a rotating star in vacuum with a dipole field. It can be especially useful as a first approximation to the electromagnetic environment of a compact star, for instance a neutron star, with an arbitrarily magnetic field.

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Time-dependent Force-free Pulsar Magnetospheres: Axisymmetric and Oblique Rotators

Cited by 825 publications

References 13 publications

Gamma-ray pulsars: A gold mine

Gamma-ray pulsars: A gold mine

R modes and neutron star recycling scenario

General solution for the vacuum electromagnetic field in the surroundings of a rotating star

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