Radiation in Astrophysical Plasmas

Zheleznyakov, V. V.

doi:10.1007/978-94-009-0201-5

Cited by 202 publications

(187 citation statements)

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“…Synchrotron self-absorption is very small at GHz and higher frequencies. For B ∼ 10 −2 G, n ∼ 0.1 cm −3 , and p ≈ 2.5, an approximate estimate for the synchrotron Zhelezniakov 1996). The corresponding optical depth through the 1-pc jet is only 2 × 10 −4 .…”

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confidence: 90%

“…On the one hand, Laing (1980Laing ( , 1981 developed detailed models for optically thin synchrotron emission from non-relativistic jets. Recently, such non-relativistic models were generalized to include plasma effects on the propagation of the radiation inside the jet, Faraday rotation and the Cotton-Mouton effect (Zheleznyakov & Koryagin 2002;Beckert & Falcke 2002;Beckert 2003;Ruszkowski 2003). In these works, although plasma is relativistic, the radiation and polarization transport are considered in a static medium.…”

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confidence: 99%

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Polarization and Structure of Relativistic Parsec-Scale AGN Jets

Lyutikov¹

2004

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Author(s)Lyutikov, M.; Pariev, V. I.; Gabuzda, Denise Publication date 2005Original citation Lyutikov, M., Pariev, V. I. and Gabuzda, D. C. (2005) ABSTRACTWe consider the polarization properties of optically thin synchrotron radiation emitted by relativistically moving electron-positron jets carrying large-scale helical magnetic fields. In our model, the jet is cylindrical and the emitting plasma moves parallel to the jet axis with a characteristic Lorentz factor . We draw attention to the strong influence that the bulk relativistic motion of the emitting relativistic particles has on the observed polarization. Our computations predict and explain the following behaviour. (i) For jets unresolved in the direction perpendicular to their direction of propagation, the position angle of the electric vector of the linear polarization has a bimodal distribution, being oriented either parallel or perpendicular to the jet. (ii) If an ultra-relativistic jet with 1 whose axis makes a small angle to the line of sight, θ ∼ 1/ , experiences a relatively small change in the direction of propagation, velocity or pitch angle of the magnetic fields, the polarization is likely to remain parallel or perpendicular; on the other hand, in some cases, the degree of polarization can exhibit large variations and the polarization position angle can experience abrupt 90• changes. This change is more likely to occur in jets with flatter spectra. (iii) In order for the jet polarization to be oriented along the jet axis, the intrinsic toroidal magnetic field (in the frame of the jet) should be of the order of or stronger than the intrinsic poloidal field; in this case, the highly relativistic motion of the jet implies that, in the observer's frame, the jet is strongly dominated by the toroidal magnetic field B φ /B z . (iv) The emission-weighted average pitch angle of the intrinsic helical field in the jet must not be too small to produce polarization along the jet axis. In force-free jets with a smooth distribution of emissivities, the emission should be generated in a limited range of radii not too close to the jet core. (v) For mildly relativistic jets, when a counter-jet can be seen, the polarization of the counter-jet is preferentially orthogonal to the axis, unless the jet is strongly dominated by the toroidal magnetic field in its rest frame. (vi) For resolved jets, the polarization pattern is not symmetric with respect to jet axis. Under certain conditions, this can be used to deduce the direction of the spin of the central object (black hole or disc), whether it is aligned or anti-aligned with the jet axis. (vii) In resolved 'cylindrical shell' type jets, the central parts of the jet are polarized along the axis, while the outer parts are polarized orthogonal to it, in accordance with observations.We conclude that large-scale magnetic fields can explain the salient polarization properties of parsec-scale AGN jets. Since the typical degrees of polarization are 15 per cent, the emitting parts of the jets must have comparable rest-fram...

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confidence: 90%

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confidence: 99%

Polarization and Structure of Relativistic Parsec-Scale AGN Jets

Lyutikov¹

2004

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“…Clearly, such effects should be taken into account while comparing theoretical neutron-star radiation models with observations. Let I ω be the specific intensity per unit circular frequency (if I ν is the specific intensity per unit frequency, then I ω = I ν /(2π); see [71]). A contribution to the observed radiation flux density from a small piece of the surface dA in the circular frequency interval [ω, ω + dω] equals [72,73] (14) where dω = (1 + z g ) dω ∞ .…”

Section: General Relativity Effectsmentioning

confidence: 99%

“…In the nonrelativistic theory, such transitions occur between the equidistant neighboring levels at the frequency ω c , which corresponds to the dipole approximation. In the relativistic theory, the multipole expansion leads to an appearance of cyclotron harmonics [71]. Absorption cross-sections at these harmonics were derived in [263] in the Born approximation without allowance for the magnetic quantization of electron motion, and represented in a compact form in [264].…”

Section: Interaction With Radiationmentioning

confidence: 99%

Atmospheres and radiating surfaces of neutron stars

Potekhin¹

2014

Phys.-Usp.

113

129

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The early 21st century witnesses a dramatic rise in the study of thermal radiation of neutron stars. Modern space telescopes have provided a wealth of valuable information which, when properly interpreted, can elucidate the physics of superdense matter in the interior of these stars. This interpretation is necessarily based on the theory of formation of neutron star thermal spectra, which, in turn, is based on plasma physics and on the understanding of radiative processes in stellar photospheres. In this paper, the current status of the theory is reviewed with particular emphasis on neutron stars with strong magnetic fields. In addition to the conventional deep (semi-infinite) atmospheres, radiative condensed surfaces of neutron stars and "thin" (finite) atmospheres are considered.

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“…To determine the ellipticity of normal modes of the radio emission in a cold anisotropic plasma, we use the following equation (Zheleznyakov 1997):…”

Section: The Model Conception Of the Propagation Mediummentioning

confidence: 99%

Investigation of the Earth Ionosphere Using the Radio Emission of Pulsars

et al. 2013

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Abstract. The investigation of the Earth ionosphere both in a quiet and a disturbed states is still desirable. Despite recent progress in its modeling and in estimating the electron concentration along the line of sight by GPS signals, the impact of the disturbed ionosphere and magnetic field on the wave propagation still remains not sufficiently understood. This is due to lack of information on the polarization of GPS signals, and due to poorly conditioned models of the ionosphere at high altitudes and strong perturbations. In this article we consider a possibility of using the data of pulsar radio emission, along with the traditional GPS system data, for the vertical and oblique sounding of the ionosphere. This approach also allows to monitor parameters of the propagation medium, such as the dispersion measure and the rotation measure using changes of the polarization between pulses. By using a selected pulsar constellation it is possible to increase the number of directions in which parameters of the ionosphere and the magnetic field can be estimated.

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Radiation in Astrophysical Plasmas

Cited by 202 publications

References 0 publications

Polarization and Structure of Relativistic Parsec-Scale AGN Jets

Polarization and Structure of Relativistic Parsec-Scale AGN Jets

Atmospheres and radiating surfaces of neutron stars

Investigation of the Earth Ionosphere Using the Radio Emission of Pulsars

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