arXiv subjects

Yuri Lyubarsky

Publications and source records attributed to Yuri Lyubarsky.

41 records · Page 3Linked to original sources

arXiv2007

Magnetic reconnection at the termination shock in a striped pulsar wind

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. 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. 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. 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. We found a very simple criterion for dissipation of alternating fields at the termination shock, depending on the upstream parameters of the flow. 1D relativistic PIC simulations are in agreement with our criterion. Thus, alternating magnetic fields annihilate easily at relativistic highly magnetised shocks.

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arXiv2006

Long Term Cooling of Magnetar Crusts

X-ray emission following giant flares of magnetars can be categorized into three categories of time scales (a) short term afterglow (b) medium term afterglow and (c) long term afterglow. Short term afterglow, which declines over several hours, seems to correspond to gravitational resettling of uplifted material. Medium term afterglow, which declines over several weeks or months, appears to be the cooling of the heated outer crust, and long term afterglow, which declines over a period of many years, can be understood to be the cooling of the inner crust. The long term afterglow profile may be a very sensitive indicator of neutron star mass.

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arXiv2006

Electron-ion coupling upstream of relativistic collisionless shocks

It is argued and demonstrated by particle-in-cell simulations that the synchrotron maser instability could develop at the front of a relativistic, magnetized shock. The instability generates strong low-frequency electromagnetic waves propagating both upstream and downstream of the shock. Upstream of the shock, these waves make electrons lag behind ions so that a longitudinal electric field arises and the electrons are accelerated up to the ion kinetic energy. Then thermalization at the shock front results in a plasma with equal temperatures of electrons and ions. Downstream of the shock, the amplitude of the maser-generated wave may exceed the strength of the shock-compressed background magnetic field. In this case the shock-accelerated particles radiate via nonlinear Compton scattering rather than via a synchrotron mechanism. The spectrum of the radiation differs, in the low-frequency band, from that of the synchrotron radiation, providing possible observational tests of the model.

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arXiv2005

Are GRB shocks mediated by the Weibel instability?

It is estimated that the Weibel instability is not generally an effective mechanism for generating ultrarelativistic astrophysical shocks. Even if the upstream magnetic field is as low as in the interstellar medium, the shock is mediated not by the Weibel instability but by the Larmor rotation of protons in the background magnetic field. Future simulations should be able to verify or falsify our conclusion.

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arXiv2003

Curvature radiation in pulsar magnetospheric plasma

We consider the curvature radiation of the point-like charge moving relativistically along curved magnetic field lines through a pulsar magnetospheric electron-positron plasma. We demonstrate that the radiation power is largely suppressed as compared with the vacuum case, but still at a considerable level, high enough to explain the observed pulsar luminosities. The emitted radiation is polarized perpendicularly to the plane of the curved magnetic filed lines coincides with $ which can freely escape from the magnetospheric plasma. Our results strongly support the coherent curvature radiation by the spark-associated solitons as a plausible mechanism of pulsar radio emission.

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