Showing papers on "Relativistic plasma published in 1973"

Collisionless damping of hydromagnetic waves in relativistic plasma. I. Weak Landau damping: heating of the Crab Nebula

Abstract: The propagation and damping of small-amplitude waves in a plasma of relativistic electrons and/or protons is studied. As in the analogous nonrelativistic problem, the damping is found to be large except for particular angles of propagation. The results are applied, in the ultrarelativistic limit, to the problem of the heating of the high-energy electrons in the Crab Nebula. Some aspects of the morphology of the propagating disturbances near the center of the nebula can be understood in terms of the magnitude and angular dependence of the calculated damping. (auth)

Relativistic Plasma and Pulsar Emission Mechanisms

Abstract: FROM the two established observation data of pulsar emission, namely, that the density of the energy flux from 1 cm2 of the surface of the emitting region (F) is extremely large (for most pulsars F≥1012 erg cm−2 s−1 and for NP 0532 F≥1020 erg cm−2 s−1); and that the maximum effective temperature of radio emission also reaches extremely large values (for most pulsars Tef ≈ 1024 K and for NP 0532 Tef, ∼ 1030 K), it necessarily follows that the plasma in the emitting region must be ultrarelativistic. We use that expression for the case when the mean energy ɛ* of all plasma particles, or at least of one component (for example all electrons), is much bigger than their rest energy mc2. This follows from the observational data1,2. First, the energy radiated comes from the particle energy and therefore we have an obvious inequality, if the emission occurs near the pulsar's surface2,3, illustration that is, illustration for most pulsars, from the radio energy losses and (1) illustration for NP 0532, from the total energy losses. Open image in new window Open image in new window Open image in new window

Nonlinear mode-mode coupling of Alfven waves in the interstellar medium

Abstract: A set of differential equations is set up to describe the temporal and spatial evolution of transverse and longitudinal waves under mode-mode coupling in a relativistic plasma embedded in an ambient magnetic field. The plasma consists of immobile protons, thermal electrons and cosmic ray protons. The cosmic rays are assumed to be streaming along the ambient magnetic field direction with a bulk velocity larger than the Alfven velocity. An Alfven wave couples with another transverse and one longitudinal wave. The temporal mode-mode coupling effects on the nonlinear behaviour of the Alfven wave (which is unstable using linear theory in the absence of mode-mode coupling) have been examined. Under certain conditions, it is found that the linear instability of the Alfven wave is 'quenched'. Upon inserting numerical parameters appropriate to the cosmic ray gas in the galactic disk it is shown that when the initial energy of perturbation is 10-2 of the ambient field energy, the rate of quenching is the same order as the linear e-folding time (10 approximately 102 yr when the streaming velocity of the cosmic ray is approximately 108 cm/sec).

A Distribution Function for the Particles in an Anisotropic Relativistic Plasma

Abstract: The particles making up a plasma are usually not in equilibrium, and their energies are often relativistic and anisotropically distributed, especially if the plasma is in a d.c. magnetic field. Thus, the usual methods for developing particle distribution functions based on equilibrium conditions are not applicable. A development of a particular anisotropic relativistic distribution function that may describe the particles in a plasma is made.

Energy conversion between longitudinal and transverse waves by mode-mode coupling in a relativistic plasma (application to Crab nebula)

Abstract: Nonlinear mode-mode coupling between a linearly unstable longitudinal oscillation and two electromagnetic waves in a spatially homogeneous, but anisotropic, relativistic plasma has been investigated in detail. The objective of doing this problem is to see if there is any 'quenching' effect on the linear instability of the longitudinal oscillation. The linear instability occurs when the relativistic component of the plasma is assumed to be a stream of high-energetic protons (cosmic rays) which possess a streaming velocity larger than the phase velocity of the longitudinal oscillation. It is found that 'the imaginary detuning factor' (which is related to the growth rate of the linear instability of the longitudinal mode) plays a dominant role in quenching the linear instability as well as in changing the wave amplitudes. For astrophysical bodies, e.g. in the vicinity of supernovae, having a thermal electron density approximately 102 cm-3 and probably a cosmic proton density approximately 10-3 cm-3 the e-folding time will be much reduced ( approximately 102-3 yr), then the quenching effect and the energy conversion between electrostatic and electromagnetic waves will be significant, with a time scale at the order of 103-4 yr. The application of these nonlinear mechanisms to the typical astrophysical radio source, the Crab nebula, has been demonstrated upon inserting numerical values.