Showing papers on "Relativistic plasma published in 1985"
TL;DR: In this article, the Rosenbluth form for the collision operator for weakly relativistic plasmas is derived and the formalism adopted by Antonsen and Chu can then be used to calculate the efficiency of current drive by fast waves in a relativist plasma.
Abstract: The Rosenbluth form for the collision operator for a weakly relativistic plasma is derived. The formalism adopted by Antonsen and Chu can then be used to calculate the efficiency of current drive by fast waves in a relativistic plasma. Accurate numerical results and analytic asymptotic limits for the efficiencies are given.
143 citations
TL;DR: In this article, a modified Korteweg-deVries (K-dV) equation was derived for ion-acoustic waves in a plasma, taking account of weakly relativistic effects.
Abstract: This is a sequel to our earlier study on ion‐acoustic waves studied through the augmentation to a modified Korteweg–deVries (K–dV) equation. We have derived a K–dV equation in a plasma, taking account of weakly relativistic effects, and the result shows that the solitary wave does exhibit the relativistic effect in the presence of ion streaming.
120 citations
TL;DR: In this paper, the excitation of plasma waves by two laser beams whose frequency difference is approximately the plasma frequency was analyzed, and the nonlinear analysis is fully relativistic in the axial and transverse directions and includes mismatching of the laser beat frequency to the plasma, time dependent laser amplitudes, and an applied transverse magnetic field (surfatron configuration).
Abstract: The excitation of plasma waves by two laser beams, whose frequency difference is approximately the plasma frequency, is analyzed. Our nonlinear analysis is fully relativistic in the axial and transverse directions and includes mismatching of the laser beat frequency to the plasma frequency, time dependent laser amplitudes, and an applied transverse magnetic field (surfatron configuration). Our analytical results for the large amplitude plasma waves include an axial constant of motion, accelerating electric field, and its phase velocity. The analytical results in the weak laser power limit are in good agreement with numerical results obtained from the complete equations. The imposed transverse magnetic field is found to increase the effective plasma frequency, but has little effect on the plasma dynamics.
58 citations
TL;DR: In this article, a kinetic theory of nonlinear Alfven solitons propagating along the equilibrium magnetic field in a relativistic electron-positron plasma is presented.
Abstract: For pt.I see ibid., vol.27, no.5, p.527-37 (1985). Kinetic theory of nonlinear Alfven waves propagating along the equilibrium magnetic field in a relativistic electron-positron plasma is presented. Comparison of the results of kinetic and hydrodynamic approaches is performed. Excitation of the Alfven solitons by a beam of high-energy particles is discussed. Results obtained are used for the interpretation of the microstructure of radio radiation of pulsars.
44 citations
TL;DR: In this paper, nonlinear Alfven solitons of moving-wave and wave-packet types were considered on the base of relativistic isotropic hydrodynamics.
Abstract: Nonlinear Alfven waves, propagating along an equilibrium magnetic field, are studied on the base of relativistic isotropic hydrodynamics. Alfven solitons of moving-wave and wave-packet type are considered. The results of Sakai and Kawata (1980) concerning the Alfven solitons of moving-wave type are revised. New expressions for the parameters characterizing these solitons are obtained.
30 citations
TL;DR: In this paper, the authors investigated the influence of multiple frequency heating on fluctuations, axial electron losses, and a scaling of these effects with power, and showed that the dominant effects are associated with an improvement in heating efficiency which persists to very small frequency separations (Δf/f∼10−3).
Abstract: High‐beta, hot‐electron plasmas have been produced by electron‐cyclotron heating in the SM‐1 axisymmetric mirror using closely‐spaced multiple frequencies. The relativistic electrons produce annular distributions (ELMO rings) with as much as ten times more stored energy than with single‐frequency heating. While larger frequency separations (Δf/f∼0.1) provide some control of the ring size, the dominant effects are associated with an improvement in heating efficiency which persists to very small frequency separations (Δf/f∼10−3). Details of the reconstruction of the ring distribution (both in steady state and during build‐up), the influence of multiple frequency heating on fluctuations, axial electron losses, and a scaling of these effects with power are presented.
29 citations
TL;DR: In this article, a novel electron distribution function is used in deriving analytic expressions for the synchrotron emissivity and absorption coefficient of relativistic loss cone and anti-loss cone distributions.
Abstract: A novel electron distribution function is used in deriving analytic expressions for the synchrotron emissivity and absorption coefficient of relativistic loss cone and anti-loss cone distributions. Under most circumstances these expressions can be written in the form of the product of the corresponding expression for an isotropic plasma and a factor due to the anisotropy. Good agreement with numerical results is found under a wide variety of conditions. The new expressions give considerable insight into the variation of the emission and absorption with various physical parameters and enable the approximate forms of actual electron distributions to be inferred from the properties of the emitted radiation. It is shown that amplification of the synchrotron continuum is impossible for loss cones with Maxwellian distributions in energy, no matter how strong their anisotropy.
25 citations
TL;DR: In this article, collision rates for arbitrary scattering cross sections are derived in the case of a beam of particles interacting with a Maxwell-Boltzmann (MB) plasma, or two MB plasmas interacting at generally different temperatures.
Abstract: Binary collision rates for arbitrary scattering cross sections are derived in the case of a beam of particles interacting with a Maxwell-Boltzmann (MB) plasma, or in the case of two MB plasmas interacting at generally different temperatures. The expressions are valid for all beam energies and plasma temperatures, from the nonrelativistic to the extreme relativistic limits. The calculated quantities include the reaction rate, the energy exchange rate, and the average rate of change of the squared transverse momentum component of a monoenergetic particle beam as a result of scatterings with particles of a MB plasma. Results are specialized to elastic scattering processes, two-temperature reaction rates, or the cold plasma limit, reproducing previous work.
21 citations
TL;DR: In this article, a model based on a synchrotron-maser instability excited by a hollow beam of moderately relativistic electrons in a plasma, in which the plasma frequency is much higher than the gyrofrequency, is proposed.
Abstract: In the literature, the emission of radiation at 2(omega sub e), where omega sub e denotes the electron plasma frequency, is usually explained as having been produced by the nonlinear interaction of two Langmuir waves via a backscattering process. Since the emission is frequently observed in solar radio bursts, the mechanism has attracted considerable theoretical interest. In the present paper a model is proposed based on a synchrotron-maser instability excited by a hollow beam of moderately relativistic electrons in a plasma, in which the plasma frequency is much higher than the gyrofrequency. An important conclusion is that, as a result of this instability, unpolarized electromagnetic waves with frequencies near 2(omega sub e) may be amplified.
19 citations
TL;DR: In this article, an expression for the ponderomotive force for relativistic particles in an arbitrary three-dimensional field configuration was derived using the covariant equations of motion (CEOM).
Abstract: Using the covariant equations of motion, an expression for the ponderomotive force is obtained for relativistic particles in an arbitrary three‐dimensional field configuration.
17 citations
TL;DR: In this paper, the absorption caused by relativistic broadening of quasiperpendicular incident waves within the second cyclotron harmonic layer is investigated in an inhomogeneous electron plasma.
Abstract: Absorption caused by relativistic broadening of quasiperpendicular incident waves within the second cyclotron harmonic layer is investigated in an inhomogeneous electron plasma. The resonance region is treated by a boundary layer analysis, and field equations valid in this region are derived by solving the rescaled (with respect to the parameter η which is the ratio of the thermal speed and the speed of light) linearized relativistic Vlasov equation. The geometrical optics solutions valid in the nonresonant region are evaluated near the resonance, and they are connected to the asymptotic forms of the inner solutions. The energy conservation theorems appropriate for this problem allow the evaluation of fractional transmitted and reflected energy, and thus distinguish between the energy mode converted to the quasielectrostatic (relativistic Bernstein) mode and that absorbed by the plasma (which does not exist for the purely perpendicular propagation and nonrelativistic case). Numerical methods are developed which enable one to handle the computation of the excessively stiff differential equations in the high‐field side. The three fundamental scattering problems are then evaluated numerically for various values of electron density and the product of electron temperature and scale length for the variation of the magnetic field for the case of perpendicular propagation. It is found that, unlike the mode coupling, the transmission of the X mode is not affected by the relativistic corrections. In the case of high‐field side incidence, the reflection is still zero as predicted in the nonrelativistic approach. However, in contrast to the zero absorption in the nonrelativistic case, there is significant absorption caused by relativistic broadening, particularly in the case of low‐field side incidence.
TL;DR: In this paper, a new method for driving relativistic plasma waves capable of ultra-high acceleration gradients (order 1GeV/cm) was presented, by injecting a single laser frequency from the side, rather than colinearly with the accelerated particles.
Abstract: A new method for driving relativistic plasma waves capable of ultra-high acceleration gradients (order 1GeV/cm) is presented. By injecting a single laser frequency from the side, rather than colinearly with the accelerated particles, both pump depletion and particle dephasing may be avoidable. The coupling of the side injected laser to the relativistic plasma wave via a pre-formed density ripple in the plasma is modelled analytically and with computer simulation.
TL;DR: In this article, the linear responce of a two-component plasma to a static test charge is analyzed at large distances from the impurity, and the results show that the electrons give the principal contribution to the response, which is long ranged and characterized by the Friedel oscillatory behavior.
Abstract: The linear responce of a two-component plasma to a static test charge is analyzed at large distances from the impurity. The electrons are considered relativistic and degenerate and the ions classical and non-relativistic. The results show that the electrons give the principal contribution to the response, which is long ranged and characterized by the Friedel oscillatory behavior.
TL;DR: In this article, the equilibrium pair concentration in an optically thin mildly relativistic plasma when copious soft photons are supplied by thermal synchrotron radiation was investigated, and it was shown that magnetic fields strengthen these restrictions considerably through the synchoretron-Compton process.
Abstract: We investigate the equilibrium pair concentration in an optically thin mildly relativistic plasma when copious soft photons are supplied by thermal synchrotron radiation. The pair equilibrium condition restricts the attainable states of a hot plasma which is supposed to exist in active galactic nuclei. There exist the maximum values for the electron temperature, the Thomson scattering depth, the size of aplasma and the strength of magnetic fields. We show that magnetic fields strengthen these restrictions considerably through the synchrotron-Compton process. For a plasma of the electron temperature higher than 8 x 10 B K, the proton density of 10 11 cm3 and the magnetic field of 10 4 G, the maximum of the Thomson scattering depth is ~ 10 and luminosity is less than ~ lO 44 erg/ sec.
TL;DR: In this paper, the effects of relativistic broadening on the propagation of waves nearly perpendicular to the equilibrium magnetic field and incident to the second electroncyclotron harmonic layer are investigated.
Abstract: Propagation of waves nearly perpendicular to the equilibrium magnetic field and incident to the second electron‐cyclotron harmonic layer is investigated in an inhomogeneous weakly relativistic plasma. The resonance region is treated by a boundary layer analysis, and the solutions are matched to the geometrical optics solutions outside the layer. This approach allows one to investigate the transmission, mode coupling, reflection, absorption, and the effects of relativistic broadening. This work extends a previous investigation with the purely perpendicular propagation. It is shown that the mode conversion and reflection rapidly cease to be of importance outside a narrow propagation cone as the doppler broadening becomes predominant. The geometrical optics approach, which breaks down in the purely perpendicular propagation, then becomes valid. It is also shown that the transmission coefficient and the reflection from the high‐field side incidence are not altered within this cone.
TL;DR: In this article, the authors investigated millimeter-wave emission from the rippled-field magnetron (cross-field free electron laser (FEL) and showed that the FEL type of instability is associated with a resonance in the particle motion of a layer of electrons embedded in the dense space charge cloud.
Abstract: Millimeter-wave emission from the rippled-field magnetron (cross-field free electron laser (FEL)) is investigated experimentally and theoretically. In this device, electrons move in quasi-circular orbits under the combined action of a radial electric field, a uniform axial magnetic field, and a radial azimuthally periodic wiggler magnetic field. In excess of 300 kW of RF power is observed in two narrow spectral lines whose frequency can be tuned continuously from ~25 to ~50 GHz by variation of the axial magnetic field. The observations are interpreted as a FEL type of instability, associated with a resonance in the particle motion of a layer of electrons embedded in the dense spacecharge cloud. The resonance is shown to occur when 2kw?0 ? (?>0/?0) ?1 -(?p/?0)2, where kw is the wiggler wavenumber, ?0 is the azimuthal electron velocity, ?0 is the relativistic cyclotron frequency in the axial magnetic field, wp is the relativistic plasma frequency, and ?0 = [1 - (?0/c)2]-1/2 of the resonant electron layer.
TL;DR: In this article, the short wavelength limit of the magnetron instability of a relativistic sharp boundary electron sheath is examined and the mode is localized to the sheath edge.
Abstract: The short wavelength limit of the magnetron instability of a relativistic sharp boundary electron sheath is examined. For short wavelengths the mode is localized to the sheath edge. This localization leads to a simple relationship (essentially a Lorentz transformation) between the relativistic and nonrelativistic growth rates. This relationship involves only equilibrium quantities evaluated at the sheath edge and explains previously noted trends that have been observed numerically.
TL;DR: In this article, an improved mathematical technique and a new code for deriving the conductivity tensor for collisionless plasmas have been developed, which is applicable to a very general case, including both hot (relativistic) and cold magnetized, with only isotropic equilibrium distributions being considered here.
TL;DR: In this article, the theory for relativistic plasma in an external helical magnetic field is reconsidered in order to study the electrostatic stability of electron beam modes, and previous recent results are then generalized.
Abstract: The theory for a relativistic plasma in an external helical magnetic field is reconsidered in order to study the electrostatic stability of electron beam modes. Previous recent results are then generalized.
Journal Article•
TL;DR: In this article, the authors calculate the spectre RX and the taux d'energies total du rayonnement de freinage electron-positron dans un plasma thermique relativiste.
Abstract: Calcul du spectre RX et du taux d'energie total du au rayonnement de freinage electron-positron dans un plasma thermique relativiste
TL;DR: In this paper, the generation and spectrum of soliton turbulence in the magnetospheric electron-positron plasma of pulsars is discussed, and the modulational instability of Langmuir waves and soliton formation are studied taking into account the low frequency Alfven waves.
Abstract: The generation and spectrum of soliton turbulence in the magnetospheric electron-positron plasma of pulsars is discussed. The modulational instability of Langmuir waves and soliton formation are studied taking into account the low frequency Alfven waves. Owing to ergodization via soliton interactions or soliton collapse, a power spectrum is found to be developed in the inertial range of turbulence. The power index is -2. The hierarchy of spatial scales has a breakdown around a length of 70 cm, which may be interpreted as the coherence length. These results are in close agreement with observed features of the pulsar radioemission. Mechanisms for the transformation of plasma turbulence into electromagnetic radiation are proposed. Specifically, the nonlinear amplification of Alfven waves is discussed. Also the emission resulting from the interaction of ultrarelativistic beams with the stochastic electric field of the solitons is studied.
TL;DR: In this paper, mode conversion near the upper-hybrid resonance frequency and electron heating was studied using a one-dimensional electromagnetic relativistic particle code, and it was found that for a sufficiently small pump field E0, E20/4πnTe ≲ 0.01, electron heating is localized in a region near the electron cyclotron layer where the pump frequency is equal to the local electron gyrofrequency.
Abstract: Mode conversion near the upper‐hybrid resonance frequency and electron heating are studied using a one‐dimensional electromagnetic relativistic particle code. It is found that for a sufficiently small pump field E0, E20/4πnTe ≲0.01, electron heating is localized in a region near the electron cyclotron layer where the pump frequency is equal to the local electron gyrofrequency. For stronger pump fields, electron heating takes place more or less uniformly across a region between the upper‐hybrid resonance layer and the cyclotron layer. In addition, a significant fraction of electromagnetic energy associated with the pump is found to be reflected back into the vacuum from a region in the plasma near the upper‐hybrid resonance layer for both strong (E20/4πnTe ≊1) and weak pumps (E20/4πnTe ≪1).
TL;DR: In this paper, a boundary layer analysis for weakly relativistic, inhomogeneous Vlasov plasma was performed and it was shown that the wave energy associated with the ordinary mode transmitted through the layer is independent of the relatvistic corrections and is given by a geometrical optics formula.
Abstract: Waves propagating nearly perpendicular to the equilibrium magnetic field across the fundamental cyclotron resonance layer are studied by a boundary layer analysis for a weakly relativistic, inhomogeneous Vlasov plasma. The plasma is assumed to be perpendicularly stratified. It is found that the wave energy associated with the ordinary mode transmitted through the layer is independent of the relativistic corrections and is given by a geometrical optics formula. It is also found that there is no reflected energy associated with this mode when it is incident from the high‐field side. These results are the same as the nonrelativistic case with purely perpendicular propagation. Relativistic effects produce a significant reduction of the reflection coefficient for low‐field side incidence from the nonrelativistic value. Correspondingly, for this mode there is a considerable increase in the absorption rate for sufficiently high, but moderate, electron density and temperature.
TL;DR: In this article, a relativistic plasma of nucleons interacting through pions via the usual isospin-invariant Yukawa coupling is analyzed in the framework of the covariant Wigner function technique.
TL;DR: In this article, the effects of weakly relativistic thermal anisotropy on the absorption profile of electromagnetic waves were examined using numerical ray-tracing techniques, and the authors showed that the presence of thermal aisotropic anisotropic radiation can actually shift the region of maximum absorption towards the electron-cyclotron resonance layer.
Abstract: Using numerical ray-tracing techniques, we study the propagation and absorption profiles of electromagnetic waves launched in the end cells of three different tandem mirrots: Phaedrus, an overdense low-temperature tandem mirror with plugs; TASKA, a conceptual tandem mirror with plugs and thermal barrier; and TMX-U, a tandem mirror with a significant hot-electron population. In particular, the effects of weakly relativistic thermal anisotropy on the absorption profile are examined. In general, at sufficiently low densities and temperatures, the X mode can access the plasma and achieve significant heating of the electrons. As the electron temperature increases, the X mode gets quickly absorbed at the edge and only the O mode achieves significant penetration and heating. For sufflciently large launching angles, the presence of thermal anisotropy can actually shift the region of maximum absorption towards the electron-cyclotron resonance layer. Regions of whistler instability appear along rays launched nearly along the machine axis, when the thermal-anisotropy ratio, temperature, and density reach sufficiently high values.
TL;DR: In this article, an analytical formulation for envelope-type solutions of intense polarized electromagnetic waves propagating in cold unmagnetized plasmas is presented, where induced charge separation is fully taken into account and nonlinearities due to mass variation of both electrons and ions are included.
Abstract: An analytical formulation is presented for envelope-type solutions of intense polarized electromagnetic waves propagating in cold unmagnetized plasmas. Induced charge separation is fully taken into account and nonlinearities due to mass variation of both electrons and ions are included. Localized solutions are found for the case of subluminous wave phase velocity. The spectrum of solutions (dependence of wave amplitude on the free parameters in the theory, phase velocity and frequency) is discussed and compared with previous analytical and numerical results.
TL;DR: In this paper, the longitudinal dielectric response function of a relativistic gas consisting of charged bosons together with the corresponding antiparticles is obtained in the random phase approximation, and an analysis of the mode structure and damping properties of the plasma is carried out.
Abstract: The longitudinal dielectric response function of a relativistic gas consisting of charged bosons together with the corresponding antiparticles is obtained in the random phase approximation. The theory is renormalized and an analysis of the mode structure and damping properties of the plasma is carried out.
TL;DR: In this paper, the thermodynamics of a classical dilute arbitrarily hot plasma in equilibrium is studied within a fully relativistic framework, and the internal energy of the plasma is calculated to all orders in KT/mc2.
Abstract: Within a fully relativistic framework, the thermodynamics of a classical dilute arbitrarily hot plasma in equilibrium is studied The internal energy of the plasma is calculated to all orders in KT/mc2 The case of a one-component plasma immersed in a static background is also studied Up to order kT/mc2 the results given previously by the authors (see ibid, vol28, p3030, 1983) are recovered On the other hand the authors also give explicit expressions for the thermodynamic functions of a high-temperature electron-positron plasma Some important questions concerning the coherence of their calculations and those of other authors are discussed
TL;DR: In this article, a thin relativistic electron layer immersed in a strong azimuthal magnetic field between two concentric cylindrical conductors is shown to be unstable.
Abstract: A thin relativistic electron layer immersed in a strong azimuthal magnetic field between two concentric cylindrical conductors is shown to be unstable. The instability is caused by the curvature of the walls, which modifies the interaction between particles in such a way that the inductive (attractive) forces are greater than the electrostatic (repulsive) forces. The growth rate of the instability peaks at long axial wavelengths.