Showing papers on "Relativistic plasma published in 1978"

Covariant Wigner function approach for relativistic quantum plasmas

Abstract: In this paper a general formalism for the treatment of relativistic quantum plasmas is given. It is manifestly covariant and rests on the use of a (covariant) relativistic Wigner function. Here it is applied to the particular case where spin effects are neglected (in most astrophysical applications this is a good approximation): a relativistic quantum Bogoliubov-Born-Green-Kirkwood-Yvan (BBGKY) hierarchy is given. The Vlasov approximation (Hartree approximation) is then considered and dispersion relations are obtained. Limiting cases (relativistic nonquantum high-temperature plasma and relativistic degenerate zero-temperature plasma) obtained previously by other authors are found anew. Finally, the formalism given appears to be much simpler and physically more transparent than many-body techniques used elsewhere.

Frequency Up-Shift for Cyclotron Wave Instability on a Relativistic Electron Beam

Abstract: The axial drift of a relativistic electron beam along a uniform magnetic field is shown theoretically to lead to significant frequency up‐shifts for linear cyclotron‐wave instabilities driven by velocity‐space anisotropy. This mechanism suggests novel means for the development of devices for generation of intense far‐infrared power.

Wave production in an ultrarelativistic electron-positron plasma

Abstract: In this paper we calculate the eigenmodes associated with an ultrarelativistic electron-positron beam traversing a low-energy electron-positron plasma under physical conditions that may exist along open magnetic field lines above pulsar polar caps. We assume that both beam and plasma are cold and charge neutral, and that magnetic field strength and particle density decrease as the cube of (1/R). In the superstrong magnetic fields near the stellar surface where cyclotron frequencies exceed plasma frequencies, electrostatic waves and associated transverse low-frequency waves are driven unstable by the two-stream type particle distribution. At larger distances above the stellar surface the slow beam cyclotron wave is driven unstable. At even greater radial distance (approximately when particle energy density exceeds magnetic energy density) both the Ordinary and Alfven modes become unstable. All of these instabilities can lead to generation of radiation. If the particle distribution as generated at the stellar surface, assumed to consist of two streams, is modified only by plasma effects, then electrostatic and associated transverse waves may only be unstable near the stellar surface. The beam cyclotron mode which is driven by a two-stream or an inverted particle distribution may be stable.

Intense microwave generation by the negative‐mass instability

Abstract: This paper examines the negative‐mass stability properties of an E layer for transverse electric (TE) and transverse magnetic (TM) waveguide modes in a conducting cylinder. The analysis is carried out for a relativistic non‐neutral E layer aligned parallel to a uniform axial magnetic field B0ez, within the context of the assumptions that the electron motion is ultrarelativistic (γ0≫1) and that (ν/γ0)1/3≪1, where ν is Budker’s parameter and γ0mc2 is the electron energy. One of the most important features of the analysis is that the axial energy spread can have a large influence on the stability behavior for both the TE and TM waveguide modes. By an appropriate choice of system parameters, it is shown that the spectrum of microwave radiation generated by the negative‐mass instability can be very narrowband.

Relativistic Boltzmann theory for a plasma: III. Viscous phenomena

Abstract: The linear laws pertaining to viscous phenomena are derived for a relativistic plasma in an electromagnetic field. The results found in this microscopic context fit precisely into the general scheme obtained on a macroscopic level by Hooyman, de Groot and Mazur.

Relativistic derivation of laser‐induced plasma profiles

Abstract: The relativistic corrections to the ponderomotive force for a general transverse plane wave of arbitrary polarization lead to an approximately twenty percent reduction in the single particle ponderomotive force for 10.6 μm CO2 light at 1016 W/cm2. The recent nonrelativistic derivation of laser‐induced plasma profiles is extended to the relativistic regime by including the relativistic corrections to the ponderomotive force in the fluid equations. Specifically, analytic results are obtained which facilitate relating the number densities and flow velocities to the electric field strength at the sonic point; in addition, these relations allow the complete self‐consistent steady state structure of the profile to be determined numerically. Several detailed comparisons of nonrelativistic and relativistic results are discussed.

Coherent radiation from an intense relativistic electron beam rotating in a background plasma

Abstract: Radiation at λ∼1 cm and megawatt power level is observed when a rotating, relativistic electron beam interacts with a background plasma. The emission spectrum is peaked at the 20th cyclotron harmonic, and the parametric dependence of the radiation is consistent with a model of interaction between single‐particle cyclotron radiation and a beam‐plasma streaming instability.

Small amplitude waves in a hot relativistic two-fluid plasma

Abstract: The dispersion relation for small amplitude waves in a hot relativistic plasma embedded in a uniform magnetic field is derived. Four plasma modes exist for propagation oblique to the magnetic field, and the mode properties are summarized in a hot relativistic generalization of the cold plasma pond diagram of Stix (1962). The two-fluid approximation is considered, and two-fluid equations are applied in this procedure which summarizes properties of linear waves in an unbounded magnetized relativistic plasma by means of a parameter-space diagram of wave phase velocity.

Collective ion acceleration through temporal modulation of relativistic-electron-beam energy

Abstract: A new method is proposed for collectively accelerating bunches of ions with an intense relativistic-electron beam. By varying the beam energy in time, acceleration of a slow Doppler-shifted cyclotron wave can be accomplished, without accompanying degradation of the beam equilibrium. Test-particle calculations employing this acceleration scheme indicate performance which is highly competitive with other collective-ion-acceleration mechanisms.

Electron energy distribution of a mirror confined relativistic plasma inferred from synchrotron radiation measurements

Abstract: Properties of a relativistic electron plasma confined in a magnetic mirror field are investigated by measuring the synchrontron radiation emitted in the 12.4–18.0 GHz frequency range. The measured spectra are recorded in a sufficiently short interval of time so that the confining magnetic field can be regarded as constant. The spectra are unfolded to obtain the electron energy distribution f (γ) during the decay of the confining magnetic field. The energy distribution obtained in this manner is compared with that calculated from a theoretical model that utilizes a self‐consistent equilibrium distribution function f0e(x,p). This model takes into account the influence of strong spatial inhomogeneities and large Larmor orbits on the emission spectrum. The comparison between theory and experiment yields information about the evolution of such quantities as the radial electron density profile, ne0(r). An analysis of the data shows that n0e(r) evolves from a relatively thin E layer to a diffuse profile with den...

What is the compact radio source in the nucleus of M82

Abstract: Observations of M82 taken over a 4 1/2 year interval with the NRAO interferometer have been analyzed to search for any variation in the compact (28 light-day) radio source, 41.9+58, at the nucleus. A decrease of 14 +- 10% between 1971 and 1975 was found, and there is no evidence for variations on a time scale of months. The relative stability of this source in view of its small size, combined with the predominance of relativistic over thermal electrons within it (/sub r//n/sub c/> or approx. =4000), indicates an acceleration mechanism that is very efficient, yet does not involve highly relativistic bulk motions. This suggests a massive rotating object with strong magnetic fields. Our very low upper limit (p/sub L/< or =0.3%) on the linear polarization of 41.9+58 in the optically thin part of its spectrum suggests that the magnetic field in this source is quite tangled.A new 8 GHzmap at 2''.2 resolution has been made, incorporating the second-epoch data, which establishes new upper limits to any linear polarization elsewhere in the nucleus of M82.

Interaction between emission-line filaments and highly energetic explosions in QSOs

Abstract: The conditions under which QSO line-emitting regions can survive a relativistic explosion are investigated along with the question of whether past and future observations can place constraints on both predicted highly energetic outbursts of ultrarelativistic plasma or LF electromagnetic radiation and the line-emitting gas. Observed properties of QSO emission-line regions are reviewed, and the interaction between a relativistic explosion and a dense cloud is analyzed for the cases of a sudden release of relativistic plasma and an outburst of LF electromagnetic waves. Bremsstrahlung X-ray emission from shocked QSO filaments is calculated, the evolution of dense QSO clouds is examined, and radiative acceleration is excluded as the process responsible for the high bulk velocities of filaments, at least in sources that display energetic outbursts. An alternative mechanism involving highly energetic explosions is proposed.

Intense relativistic electron-beam trajectories and their effect on beam heating of toroidally confined plasma

Abstract: The trajectories of an intense relativistic electron beam propagating between a toroidal plasma column and a conducting vacuum wall are calculated theoretically and verified experimentally. Three classes of trajectories are observed, including a set of banana‐type orbits. The significance of these trajectories on the ability of the beam to transfer energy to the plasma is discussed.