Lack of an analogue of the Crab Nebula around PSR1937 + 214 is shown to be consistent with theory of pulsar magnetospheres only if the surface magnetic field is unusually weak, ∼109 G. Predictions are made for observations of the weak nebular emission around this object. It is suggested that the neutron star was born as a weakly magnetized, rapidly rotating pulsar, and now is 105–106 yr old.

On the magnetization and origin of the millisecond pulsar 1937 + 214

A general dispersion relation is derived for a plasma in a helical magnetic field of arbitrarily large amplitude. Comparisons are made with previous results for large amplitude waves emitted by pulsars as well as for the free electron laser. Discrepancies between the present new coupling coefficients and those of previous authors are pointed out and explained.

On the Stability of a Magnetized Plasma in a Large Amplitude Circularly Polarized Wave

Rotating, compact objects power some of the most spectacular phenomena in astrophysics, e.g., gamma-ray bursts, active galactic nuclei and pulsar winds. The energy is carried by Poynting flux, and the system is usually modelled using relativistic magnetohydrodynamics (MHD). However, in the relatively low density medium expected around some of these objects, the MHD approximation breaks down, allowing new, large-amplitude waves to propagate. We discuss the role of these waves in two astrophysical contexts: In blazar jets, we show that a magnetic shear, launched together with a plasma from the black hole magnetosphere, begins to accelerate particles at a large distance from its source. The resulting non-thermal emission can, nevertheless, be modulated on very short timescales, which can explain the rapid variability of the TeV gamma-ray flux observed from some blazars. In pulsar winds, we analyze the radial propagation of superluminal modes, including their damping by radiation reaction and by interaction with an external photon field. We discuss their effect on the structure of the pulsar wind termination shock, presenting new solutions in which the non-linear wave is asymptotically matched to the constant pressure surroundings. The observational implications of these solutions are discussed for both isolated pulsars, and pulsars in binary systems.

Nonlinear waves in Poynting-flux dominated outflows

Etude de 2 types d'onde non lineaire dans des plasmas d'electrons non magnetises froids: onde longitudinale stationnaire etablie par des faisceaux d'electrons froids a contre-courant, onde stationnaire longitudinale-transversale dans un plasma relativiste

A comparative study of the instabilities of two classes of nonlinear waves in cold plasmas

We consider the stability against small perturbations of a class of exact wave solutions of the equations that describe an unmagnetized relativistic cold electron plasma. The main feature of these nonlinear waves is a transverse circularly polarized electric field with periodic amplitude modulation in the longitudinal direction. Floquet's theory of linear differential equations with periodic coefficients is used to solve the perturbation equations and obtain the instability growth rates.

Stability of strong electromagnetic waves in overdense plasmas

This is part 2 of a paper concerned with the stability against small perturbations of a certain class of nonlinear wave solutions of the equations that describe a cold unmagnetized plasma. It refers to transverse linearly polarized waves in an electron-positron plasma. A numerical method, based on Floquet's theory of linear differential equations with periodic coefficients, is used to solve the perturbation equations and obtain the instability growth rates. All the three possible types of perturbations are discussed for a typical value of the (large) amplitude of the nonlinear wave: electrically longitudinal slightly unstable modes (with maximum growth rate γ approximately equal to 0·07ω 0 , where ω 0 is the frequency of the nonlinear wave); purely transverse moderately unstable modes (with γ ≃ 0·26ω 0 ); and highly unstable electrically transverse modes (with γ ≃ l·5ω 0 ).

Stability of relativistic transverse cold plasma waves Part 1. Circularly polarized waves

Relation de dispersion pour les perturbations aux grandes longueurs d'onde d'une classe d'ondes non lineaires. L'analyse de la relation de dispersion montre que les ondes non lineaires avec modulation periodique deviee sont toujours instables; celles avec modulation periodique non deviee sont stables dans la region de l'espace des parametres ou elles existent; celles avec modulation aperiodique du type solitaire sont aussi stables

F. J. Romeiras

Papers

Stability of relativistic transverse cold plasma waves Part 1. Circularly polarized waves

Stability of strong electromagnetic waves in overdense plasmas

Stability of strong electromagnetic waves in overdense plasmas against long-wavelength perturbations