56 research outputs found
Emission Mechanisms of Fast Radio Bursts
Fast radio bursts (FRBs) are recently discovered mysterious single pulses of
radio emission, mostly coming from cosmological distances ( Gpc). Their
short duration, ms, and large luminosity evidence coherent emission. I
review the basic physics of coherent emission mechanisms proposed for FRBs. In
particular, I discuss the curvature emission of bunches, the synchrotron maser,
and the emission of radio waves by variable currents in the course of magnetic
reconnection. Special attention is paid to magnetar flares as the most
promising sources of FRBs. Non-linear effects are outlined that could place
bounds on the power of the outgoing radiation.Comment: To be published in Univers
On the escape of low-frequency waves from magnetospheres of neutron stars
We study the nonlinear decay of the fast magnetosonic into the Alfv\'en waves
in relativistic force-free magnetohydrodynamics. The work has been motivated by
models of pulsar radio emission and fast radio bursts (FRBs), in which the
emission is generated in neutron star magnetospheres at conditions when not
only the Larmor but also the plasma frequencies significantly exceed the
radiation frequency. The decay process places limits on the source luminosity
in these models. We estimated the decay rate and showed that the phase volume
of Alfv\'en waves available for the decay of an fms wave is infinite. Therefore
the energy of fms waves could be completely transferred to the small-scale
Alfv\'en waves not via a cascade, as in the Kolmogorov turbulence, but
directly. Our results explain the anomalously low radio efficiency of the Crab
pulsar and show that FRBs could not be produced well within magnetar
magnetospheres.Comment: ApJ, in pres
Radiatively driven evaporation from magnetar's surface
The luminosity of the Soft Gamma Repeater (SGR) flares significantly exceeds
the Eddington luminosity. This is because they emit mainly in the E-mode, for
which the radiative cross-sections are strongly suppressed. The energy is
released in the magnetosphere forming a magnetically trapped pair fireball, and
the surface of the star is illuminated by the powerful radiation from the
fireball. We study the ablation of the matter from the surface by this
radiation. The E-mode photons are scattered within the surface layer, partly
being converted into O-photons, whose scattering cross-section is of the order
of the Thomson cross-section. The high radiation pressure of the O-mode
radiation expels the plasma upwards. The uplifted matter forms a thick baryon
sheath around the fireball. If an illuminated fraction of the star's surface
includes the polar cap, a heavy, mildly relativistic baryonic wind is formed.Comment: 11 pages, 5 figure
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