The termination shock in a striped pulsar wind

Lyubarsky, Yuri

doi:10.1016/j.asr.2005.01.025

Cited by 26 publications

(27 citation statements)

References 36 publications

(71 reference statements)

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“…Electromagnetic waves leave the simulation box at the right boundary without any reflection. Similar simulations have already been performed by Lyubarsky (2005b).…”

Section: Termination Shock: Pic Simulationssupporting

confidence: 69%

Magnetic reconnection at the termination shock in a striped pulsar wind

Pétri

Lyubarsky

2007

A&A

118

115

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Context. Most of the rotational luminosity of a pulsar is carried away by a relativistic magnetised wind in which the matter energy flux is negligible compared to the Poynting flux. However, observations of the Crab nebula for instance clearly indicate that most of the Poynting flux is eventually converted into ultra-relativistic particles. The mechanism responsible for transformation of the electro-magnetic energy into the particle energy remains poorly understood. Near the equatorial plane of an obliquely rotating pulsar magnetosphere, the magnetic field reverses polarity with the pulsar period, forming a wind with oppositely directed field lines. This structure is called a striped wind; dissipation of alternating fields in the striped wind is the object of our study. Aims. The aim of this paper is to study the conditions required for magnetic energy release at the termination shock of the striped pulsar wind. Magnetic reconnection is considered via analytical methods and 1D relativistic PIC simulations.Methods. An analytical condition on the upstream parameters for partial and full magnetic reconnection is derived from the conservation laws of energy, momentum and particle number density across the relativistic shock. Furthermore, by using a 1D relativistic PIC code, we study in detail the reconnection process at the termination shock for different upstream Lorentz factors and magnetisations. Results. We found a very simple criterion for dissipation of alternating fields at the termination shock, depending on the upstream parameters of the flow, namely, the magnetisation σ, the Larmor radius r B and the wavelength l of the striped wind. The model depends also on a free parameter ξ > 1, which is the ratio of the current sheet width to the particle Larmor radius. It is found that for σ l/ξ r B , all the Poynting flux is converted into particle energy whereas for σ (l/ξ r B ) 2/3 , no dissipation occurs. In the latter case, the shock can be accurately described by the ideal MHD shock conditions. Finally, 1D relativistic PIC simulations confirm this prediction and enable us to fix the free parameter ξ in the analytical model. Conclusions. Alternating magnetic fields annihilate easily at relativistic highly magnetised shocks. In plerions, our condition for full magnetic dissipation is satisfied at the termination shock so that the Poynting flux may be converted into ultra-relativistic particles not in the pulsar wind but just at the termination shock. The constraints are more severe for the intra-binary shocks in double pulsar systems. Available models explaining observations require low magnetisation in the downstream flow. The condition that the magnetic field dissipates at the intra-binary shock implies an upper limit on the pair multiplicity in the pulsar wind κ. We found κ few × 10 4 for PSR 1259-63 and PSR 1957+20. In the double pulsar PSR 0737-3039, the radio emission from the pulsar B is modulated with the period of the pulsar A, which implies that the striped structure is not erased completely; th...

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“…Electromagnetic waves leave the simulation box at the right boundary without any reflection. Similar simulations have already been performed by Lyubarsky (2005b).…”

Section: Termination Shock: Pic Simulationssupporting

confidence: 69%

Magnetic reconnection at the termination shock in a striped pulsar wind

Pétri

Lyubarsky

2007

A&A

118

115

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“…As the result, relative to the shocked plasma the shock propagates at speed well below the speed of light but close to that of a shock in ultra-relativistic unmagnetized plasma, v s c/3. The role of magnetic dissipation of the shock speed has been studied theoretically by Lyubarsky (2003) In the following, we discuss the results of driven evolution of ABC structure using both fluid and PIC simulations. We find that using both fluid and PIC codes, that imposing finite amplitude perturbations from the beginning triggers the instability much faster.…”

Section: Driven Evolution Of a System Of Magnetic Islandsmentioning

confidence: 99%

Particle acceleration in relativistic magnetic flux-merging events

et al. 2017

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(Received xx; revised xx; accepted xx)Using analytical and numerical methods (fluid and particle-in-cell simulations) we study a number of model problems involving merger of magnetic flux tubes in relativistic magnetically-dominated plasma. Mergers of current-carrying flux tubes (exemplified by the two dimensional "ABC" structures) and zero total current magnetic flux tubes are considered. In all cases regimes of spontaneous and driven evolution are investigated.We identify two stages of particle acceleration during flux mergers: (i) fast explosive prompt X-point collapse and (ii) ensuing island merger. The fastest acceleration occurs during the initial catastrophic X-point collapse, with the reconnection electric field of the order of the magnetic field. During the X-point collapse particles are accelerated by charge-starved electric fields, which can reach (and even exceed) values of the local magnetic field. The explosive stage of reconnection produces non-thermal power-law tails with slopes that depend on the average magnetization σ. For plasma magnetization σ 10 2 the spectrum power law index is p > 2; in this case the maximal energy depends linearly on the size of the reconnecting islands. For higher magnetization, σ 10 2 , the spectra are hard, p < 2, yet the maximal energy γ max can still exceed the average magnetic energy per particle, ∼ σ, by orders of magnitude (if p is not too close to unity). The X-point collapse stage is followed by magnetic island merger that dissipates a large fraction of the initial magnetic energy in a regime of forced magnetic reconnection, further accelerating the particles, but proceeds at a slower reconnection rate.

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“…Dissipation around the termination shock may also support efficient particle acceleration in two ways: by seeding large scale turbulence, causally disconnected from the upstream magnetic topology, in which case particle acceleration could proceed unimpeded [62]; or, by providing an extra mechanism of particle acceleration, which would feed into the Fermi process at higher energies, e.g. through the dissipation of MHD waves [68], or reconnection [69][70][71]. Furthermore, the MHD simulations of Ref.…”

Section: General Input From the Crab Nebulamentioning

confidence: 99%

On ultra-high energy cosmic ray acceleration at the termination shock of young pulsar winds

Lemoine

Kotera

Pétri

2015

J. Cosmol. Astropart. Phys.

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Pulsar wind nebulae (PWNe) are outstanding accelerators in Nature, in the sense that they accelerate electrons up to the radiation reaction limit. Motivated by this observation, this paper examines the possibility that young pulsar wind nebulae can accelerate ions to ultra-high energies at the termination shock of the pulsar wind. We consider here powerful PWNe, fed by pulsars born with ∼ millisecond periods. Assuming that such pulsars exist, at least during a few years after the birth of the neutron star, and that they inject ions into the wind, we find that protons could be accelerated up to energies of the order of the Greisen-Zatsepin-Kuzmin cut-off, for a fiducial rotation period P ∼ 1 msec and a pulsar magnetic field B ∼ 10 13 G, implying a fiducial wind luminosity L p ∼ 10 45 erg/s and a spin-down time t sd ∼ 3 × 10 7 s. The main limiting factor is set by synchrotron losses in the nebula and by the size of the termination shock; ions with Z ≥ 1 may therefore be accelerated to even higher energies. We derive an associated neutrino flux produced by interactions in the source region. For a proton-dominated composition, our maximum flux lies slightly below the 5-year sensitivity of IceCube-86 and above the 3-year sensitivity of the projected Askaryan Radio Array. It might thus become detectable in the next decade, depending on the exact level of contribution of these millisecond pulsar wind nebulae to the ultra-high energy cosmic ray flux.

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The termination shock in a striped pulsar wind

Cited by 26 publications

References 36 publications

Magnetic reconnection at the termination shock in a striped pulsar wind

Magnetic reconnection at the termination shock in a striped pulsar wind

Particle acceleration in relativistic magnetic flux-merging events

On ultra-high energy cosmic ray acceleration at the termination shock of young pulsar winds

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