High-Energy Astrophysics American and Soviet Perspectives/Proceedings from the U.S.-U.S.S.R. Workshop on High-Energy Astrophysics (1991) / Chapter Skim
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ON THE NATURE OF PULSAR RADIATION
ON THE NATURE OF PULSAR RADIATION
Pages 225-236
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From page 225... ...
A spinning magnetized neutron star generates the electric field which extracts electrons from the star surface and accelerates them forming low density (nb = 710-2 BoP~i, where P is the pulsar period and Be the magnetic field at the star surface) and the energetic (the Lorentz-factor of particles is orb = 3.106 .
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From page 226... ...
of the particles momenta p ~ decay, and the distribution function tends to be one-dimensional. Most probably the magnetic field near the pulsar has a complicated structure differing greatly from a dipole.
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From page 227... ...
In the electron-positron plasma deserted by (j, there exists two types of waves: the purely transversal electromagnetic t-wave with an electric vector Et directed transversely to the plane where the magnetic force line lies, and the potential-nonpotential it-wave with the electric field Elf in the plane of k and Bo. The spectra of me waves are as follows:
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From page 228... ...
The pulsar emission mechanisms provide information on wave excitation and propagation in the magnetosphere plasma along with their emergence in vacuum. The electromagnetic waves leave the magnetosphere without transformation.
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From page 229... ...
Assuming that the electron and positron distribution functions are about the same, and considering the perturbations propagating nearly along the magnetic field in the k ~ v ~ /wB ~ 1 approximation one obtains the following dispersion relation for t-waves: k2c2 2 = e== Cat (7) For the development of the cyclotron instability it is necessary to satyr the following conditions (Machabeli and Usov 1979~: 1.
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From page 230... ...
On the other hand it seems more probable that the magnetic field of a neutron star near the stellar surface differs greatly from the dipole one, and the curvature of the field lines RB is on the order of Ro (Ruderman and Sutherland 1975~. Observational data on pulsars (Davies e!
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From page 231... ...
Let us consider the possibility of the t-wave excitation by the beam particles at a Cherenkov resonance (Kazbegi et al.
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(19~. Note that when k ~ ~ O it- and l-waves turn into one purely electromagnetic branch describing the perturbations with an arbitrary polarization.
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The excited waves propagate along the magnetic force lines with k' ~ O producing the "core"-~e emission Note that this mechanism is most stable among the others and can be applied to the young pulsars. The development of the cyclotron instability is accompanied by the quasilinear diffusion of waves with the energetic particles.
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From page 234... ...
The range of emitted frequencies generated at cyclotron instability decrease with the pulsar slow-down and if P > 0.1 0.2s the frequency range will lower to radio frequencies and soft X-rays or UV (for radiation produced by synchrotron mechanism)
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From page 235... ...
1989a) the only plasma instabilities are: the cyclotron developing at the anomalous Doppler-effect resonance; and Cherenkov with the consideration of the particle transversal momenta caused by the quasilinear diffusion in one case and by the drift motion in the other one.
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From page 236... ...
236 AMERICAN AND SOVIET PERSPECTIVES Rude~man, M.A, and P.G. Sutherland.
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