Showing papers on "Relativistic plasma published in 1979"

A theory of subpulse polarization patterns from radio pulsars.

Abstract: We consider the effect of the magnetoactive plasma on the subpulse polarization patterns from radio pulsars. The radiation is presumed to originate from a very relativistic plasma streaming out along open field lines, either from curvature acceleration of charge bunches or from the acceleration parallel to the guiding magnetic field associated with the formation of the bunches. The different polarizations of subpulse rays within a relativistically narrowed emission cone are ordered by adiabatic walking as the curved magnetic field lines bend slowly out of the emission cone in the near magnetosphere. Essentially 100% polarization averaged over the rays within the emission cone can be achieved even if the initial average polarization over these rays is very much less or even zero. Sudden orthogonal mode transitions appear to have a natural explanation. Expected asymmetries between the posively and negatively charged components of the magnetoactive plasma would introduce circular polarization components into the polarization pattern even while adiabatic walking continues in the far magnetosphere. These give rise to promising models for describing the rich variety of elliptical polarization and rapid position-angle variation seen in some subpulses.

Particle reacceleration in radio galaxies

Abstract: The magnetohydrodynamic wave spectra expected in a plasma cloud moving through an external gas are derived using the drag of that gas, coupled through surface instabilities, as the energy source and microscopic damping as the energy drain. Using these spectra, the reacceleration rate of relativistic particles is calculated. It turns out that plasma clouds with high initial kinetic energy can reaccelerate the radio synchrotron-emitting particles fast enough to overcome synchrotron losses but that the process is inefficient and most of the kinetic energy goes into heating of the background gas.

Stimulated backscattering from relativistic unmagnetized electron beams

Abstract: Analysis of stimulated scattering of a high‐frequency incident pump wave from an unmagnetized relativistic electron beam is presented The backscattered radiation frequency can be enhanced by the factor 4γ20 over the incident pump frequency, where γ0 is the relativistic factor of the electron beam The linear growth rates associated with the wave‐wave and wave‐particle modes of scattering, in the high gain limit, are examined for a number of different pump amplitude regimes Estimates for the scattering efficiency are presented for the wave‐wave scattering process

Finite Larmor radius effects in the absorption of electromagnetic waves around the electron cyclotron frequency

Abstract: The role of finite Larmor radius effects in the absorption of the extraordinary and ordinary mode at frequencies around the electron cyclotron frequency by a weakly relativistic thermal plasma of finite density is investigated. An inconsistent approximation regarding the absorption of the extraordinary mode at perpendicular propagation is corrected.

Energy loss due to binary collisions in a relativistic plasma

Abstract: Energy-transfer equations for a test particle in a fully ionized plasma are presented. The charged particles interact via Lienard-Wiechert potentials and the dominant contribution to the scatterings are from small-angle binary collisions. Asymptotic expansions of the energy rate equations are presented for all cases where either the test or the field particles or both are relativistic. These asymptotic equations are then used to derive equations determining rates of equipartition of energy, from which appropriate equipartition times are deduced. This work represents a relativistic generalization of nonrelativistic binary-collision Coulomb scattering.

Absorption around the electron cyclotron frequency in a thermal plasma of finite density

Abstract: Cyclotron absorption around the electron cyclotron frequency in a weakly relativistic plasma of finite density in thermal equilibrium is considered for both perpendicular and quasi-perpendicular propagation. A comprehensive analysis which includes thermal effects together with finite density corrections is given and the resulting scaling of the absorption of the extraordinary and the ordinary modes is examined. The line profiles are discussed and the optical thicknesses of a typical tokamak plasma are evaluated.

Radiative collapse of a relativistic electron-positron plasma to ultrahigh densities

Abstract: It is shown that a relativistic electron-positron plasma formed by the coalescence of two counterstreaming intense relativistic electron and positron beams can collapse into a very-small-diameter filament. The collapse is accompanied by the emission of intense coherent $\ensuremath{\gamma}$ radiation. The radius of the collapsed state is determined by the quantum-mechanical uncertainty principle. At its maximum contraction the electron-positron plasma can approach nuclear densities. The predicted effect may have many interesting applications, some of which are briefly mentioned. The generation of the intense beams seems to be possible with existing techniques.

Current responses of all orders in a collisionless plasma. I. General theory

Abstract: An arbitrary electromagnetic perturbation of a general solution of the relativistic Vlasov–Maxwell equations is considered The nonlinear current responses are expressed in a form which in particular is an all order manifestation of the Manley–Rowe relations A coordinate free formalism is used, starting with a representation of Minkowski space in terms of abstract linear algebra, and all formulas are intrinsically covariant In the method used to derive the current responses the perturbation of particle orbits rather than of distribution functions is calculated

Longitudinal waves and two-stream instability in a relativistic plasma

Abstract: We investigate the problem of longitudinal waves in a relativistic plasma, with phase velocity lower than the velocity of light. We show that such waves exist at arbitrary particle momentum distribution function that falls off rapidly enough at large momenta. Earlier papers dealing with these questions are analyzed in connection with the problem of pulsar radiation, and the causes of the unclear and confused views advanced in some of these papers are discussed. Relativistic-plasma instabilities due to Cerenkov buildup of longitudinal waves by beams of high-energy and low-energy particles are investigated. The quasilinear relaxation of a beam of high-energy particles in a relativistic plasma is considered and the main regularities of this relaxation are explained.

Cyclotron Maser Instability for Intense Solid Electron Beams

Abstract: The cyclotron maser instability for a solid relativistic electron beam propagating parallel to a uniform axial magnetic field B0?z is investigated. The stability analysis is carried out within the framework of the linearized Vlasov‐Maxwell equations. It is assumed that ν/?≪1, where ν is Budker’s parameter and ?mc2 is the electron energy. Stability properties are investigated for the choice of equilibrium distribution function in which all electrons have the same value of total perpendicular energy, the same value of axial velocity, and a step‐function distribution in canonical angular momentum. The instability growth rate is calculated including a determination of the optimum value of the beam radius R0 for maximum growth. It is found that the maximum growth rate for a solid beam is comparable to the maximum growth rate for a hollow beam.

Langmuir turbulence of a relativistic plasma in a strong magnetic field

Abstract: We study the Langmuir turbulence of a relativistic plasma in a strong magnetic field. We obtain the equations which describe this turbulence and analyze them qualitatively in the strongly relativistic approximation. We assume that the Langmuir oscillations are excited by two-stream instability. We consider the cases of an electron-positron and an electron-ion plasma. We show that the main result of the nonlinear scattering of the waves excited due to a beam instability in an ultrarelativistic plasma is the absorption of oscillatory energy by the particles. The accumulation of long-wavelength Langmuir oscillations (the condensate) which is important in the theory of a nonrelativistic plasma is appreciably reduced. We conclude that, as in the nonrelativistic case, the dynamics of the beam instability is characterized by two consecutive stages: the quasilinear and the nonlinear ones. We show that these two stages last for times of the same order of magnitude.

The Relativistic Boltzmann Equation and the Equations of Magnetohydrodynamics with Radiative Reaction

Abstract: The relativistic collisionless Boltzmann equation with radiative reaction is derived from the conservation of the number of particles in the reduced six-dimensional phase space. It is then written in a covariant form. By taking invariant moments of the Boltzmann equation, we obtain the system of equations for relativistic magnetohydrodynamics taking account of radiative reaction. 21 and others have demonstrated that, for ultrarelativistic par­ ticles, the radiative reaction force can, in fact, be much greater than the Lorentz force. We have also shown explicitly that radiative reaction, although negligible at low temperatures, becomes dominant in the region of extremely high effective temperatures in our studies of relativistic plasma oscillations. 31 This suggests the necessity of including the force of radiative reaction in many astrophysical problems when the effective temperatures are extremely high. In the present work, we shall derive the relativistic Boltzmann equation and the equations of magnetohydro­ dynamics with radiative reaction taken into account. The formulation used here is similar to that of Goto, 41 and that of our previous work on relativistic classical scalar :fluid. 51 " 61

Scattering of radiation by finite volumes of relativistic plasma streams

Abstract: The spectrum is found for the radiation scattered by single particles in a finite volume of a relativistic plasma or plasma stream which is singled out by the optical system.

Interaction of a relativistic electron beam with surface waves

Abstract: The electromagnetic surface modes at the interface between two plasma media are studied and the excitation of these surface waves in a plasma by a relativistic electron beam is discussed. Under the resonance condition ω?kzvb, it is shown that an electron beam crossing a plasma can excite a surface electromagnetic wave at the plasma frequency ω=ωp.

Current responses of all orders in a collisionless plasma. II. Homogeneous plasma

Abstract: Expressions for the admittance tensors of all orders are obtained for a relativistic magnetized Vlasov–Maxwell plasma. Symmetries, from which the Manley–Rowe relations follow, are explicit in the expressions obtained. The treatment is covariant.

Statistical mechanics of relativistic plasmas

Abstract: Based on the Klimontovich method of construction of a relativistic statistical mechanics the binary correlation function of a relativistic plasma is considered. Up to the order e4 for spatially homogeneous systems the relativistic binary correlation function can be expressed by the relativistic dielectric tensor, where higher-order correlation functions are neglected. In the case of thermodynamic equilibrium the relativistic dielectric tensor is calculated. The corresponding binary correlation function is determined up to the first relativistic order. The result is compared with those of Trubnikov/Kosachev (1968) and Krizan (1969).

Nuclear gamma-ray lines from Cen A: Evidence for their origin in relativistic plasma

Abstract: An analysis of the experimental data on nuclear gamma-ray lines from Cen A reveals essential energetic difficulties, associated with the usual interpretation of these lines as a result of interactions of subcosmic rays with interstellar gas; since the necessary instantaneous energy loss rate of the cosmic rays should reach tremendous values of about 1048–1049 ergs s−1. These difficulties are eliminated if the gamma rays are produced in the relativistic non-isothermal plasma near a compact source of activity — such as a massive black hole or a magnetoid (spinar).

The Hierarchy of Instabilities in Pulsar Plasma

Abstract: The Tsytovich--Kaplan proposal that cyclotron Alfven instability represents the most important instability in pulsar plasma is reconsidered by analyzing an electron--positron plasma. In such plasma, which is currently believed to exist in pulsars, the cyclotron Alfven instability predicted for electron--ion plasma will not develop. Accordingly, the most important instability in pulsar plasma should be two-stream Cerenkov instability.