On a mechanism of magnetic field generation in pulsars

We describe the microphysics, phenomenology, and astrophysical implication of a B-field induced unpairing effect that may occur in magnetars, if the local B-field in the core of a magnetar exceeds a critical value Hc2. Using the Ginzburg-Landau theory of superconductivity, we derive the Hc2 field for proton condensate taking into the correction (≤ 30%) which arises from its coupling to the background neutron condensate. The density dependence of pairing of proton condensate implies that Hc2 is maximal at the crust-core interface and decreases towards the center of the star. As a consequence, magnetar cores with homogenous constant fields will be partially superconducting for "medium-field" magnetars (10 15 ≤ B ≤ 5 × 10 16 G) whereas "strong-field" magnetars (B > 5 × 10 16 G) will be void of superconductivity. The neutrino emissivity of a magnetar's core changes in a twofold manner: (i) the B-field assisted direct Urca process is enhanced by orders of magnitude, because of the unpairing effect in regions where B ≥ Hc2; (ii) the Cooper-pair breaking processes on protons vanish in these regions and the overall emissivity by the pair-breaking processes is reduced by a factor of only a few.

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“…[11]. The entrainment effect describes the current-current coupling between the neutron and proton condensates.…”

Section: Ginzburg-landau Theory Of Hc2 In Dense Mattermentioning

confidence: 99%

Magnetar superconductivity versus magnetism: Neutrino cooling processes

Sinha

Sedrakian

2015

Phys. Rev. C

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“…Assuming that (unlike what would be required for a model of "transfusive" type [1]) there is no algebraical constraint on the momenta, it can be seen (by contracting the relevant force formulae (27) and (28) with the corresponding current vectors) that for the cases of the neutrons and the protons the conditions (37) include the implication that their currents are separately conserved,…”

Section: Three Constituent Perfectly Conducting Fluidsmentioning

confidence: 99%

“…The formula (98), with α p n given by the final expression in (94), is already familiar from the corresponding analysis in a Newtonian framework [27,28]. If the "Meissner effect" were fully effective the residual flux term would tend to zero, but as was originally realised by London in the context of ordinary metallic superconductivity this can be expected only in a strictly static background, whereas more generally even in a stationary case provided the background is rotating, there will be a residual magnetic field even at large distances from a vortex, It is important to point out that this result differs from the result obtained in the Newtonian limit by Mendell [7], who found the polarisation to be zero.…”

mentioning

confidence: 99%

Relativistic models for superconducting-superfluid mixtures

1998

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Abstract:The material below the crust of a neutron star is understood to be describable in terms of three principal independently moving constituents, identifiable as neutrons, protons, and electrons, of which the first two are believed to form mutually coupled bosonic condensates. The large scale comportment of such a system will be that of a positively charged superconducting superfluid in a negatively charged "normal" fluid background. As a contribution to the development of the theory of such a system, the present work shows how, subject to neglect of dissipative effects, it is possible to set up an elegant category of simplified but fully relativistic three-constituent superconducting superfluid models whose purpose is to provide realistic approximations for cases in which a strictly conservative treatment is sufficient. A "mesoscopic" model, describing the fluid between the vortices, is constructed, as well as a "macroscopic" model taking into account the average effect of quantised vortices.

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“…In carrying out the Ginzburg-Landau expansion (2) we have taken into account (assuming second order phase transition) that the pre-factor of the |ψ| 2 term changes its sign at T c , therefore it can be expanded in the small parameter τ to leading order. The current-current coupling, i.e., the entrainment of the proton condensate by the neutron condensate, can be absorbed in the effective gauge potential A [10,14].…”

Section: Critical Unpairing Of Proton Condensatementioning

confidence: 99%

“…Note that the thermodynamical magnetic field H cm has no physical significance for type-II superconductors, which exist between the lower H c1 and upper H c2 critical fields. The GL theory of neutron-proton superfluid mixtures is based on the functional [14,15,16]…”

Section: Critical Unpairing Of Proton Condensatementioning

confidence: 99%

From microphysics to dynamics of magnetars

Sedrakian

Huang

Sinha

et al. 2017

J. Phys.: Conf. Ser.

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Abstract. MeV-scale magnetic fields in the interiors of magnetars suppress the pairing of neutrons and protons in the S-wave state. In the case of a neutron condensate the suppression is the consequence of the Pauli-paramagnetism of the neutron gas, i.e., the alignment of the neutron spins along the magnetic field. The proton S-wave pairing is suppressed because of the Landau diamagnetic currents of protons induced by the field. The Ginzburg-Landau and BCS theories of the critical magnetic fields for unpairing are reviewed. The macrophysical implications of the suppression (unpairing) of the condensates are discussed for the rotational crust-core coupling in magnetars and the neutrino-dominated cooling era of their thermal evolution.

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On a mechanism of magnetic field generation in pulsars

Cited by 8 publications

References 5 publications

Magnetar superconductivity versus magnetism: Neutrino cooling processes

Magnetar superconductivity versus magnetism: Neutrino cooling processes

Relativistic models for superconducting-superfluid mixtures

From microphysics to dynamics of magnetars

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