摘要:

A current‐carrying electron‐proton plasma is studied by calculating the velocity distribution of the particles with the Lenard‐Balescu‐Guernsey form of the Fokker‐Planck equations rather than with the familiar Landau form. The Landau equations yield velocity distributions that become unstable to longitudinal ion waves when the temperature ratioTe/Tiis large and the electric fieldE0that drives the current exceeds a critical magnitudeEcrit. The Landau equations are then not appropriate because they do not include the effect that the fluctuations associated with these ion waves have upon the velocity distributions. The Lenard‐Balescu‐Guernsey equations show that asE0is increased towardEcritthese fluctuations increase and affect the electron velocity distribution much as enhanced electron‐electron collisions would do. In particular, this nonlinear process reduces the electrical conductivity by a noticeable amount (a few percent in the examples given). Although one might also expect the threshold electric field for instability to be increased significantly, this effect is found to be extremely weak, if it exists.

ISSN:0031-9171    

DOI:10.1063/1.1762176

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The properties of the Fourier‐Hermite transformation of the one‐dimensional Vlasov equation for the motion of electrons against a uniform positive neutralizing background are examined in the linearized limit. The general dispersion relation is presented for the transformed equations. Numerical and analytical results are given which show the recovery of Landau damping for Maxwell's distribution even though the corresponding eigenfrequencies are always real. An example of double streaming is treated to show the appearance of imaginary eigenfrequencies in the analysis. Introduction of a small number of collisions is shown to improve the long‐term behavior. Nonlinear numerical results for the nearly cold plasma are shown to agree with the exact treatment of Kalman.

ISSN:0031-9171    

DOI:10.1063/1.1762177

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The Bhatnagar‐Gross‐Krook equations are used to obtain the steady‐state velocity distribution for a uniform, fully ionized plasma in a dc electric field. The Joule heating of the plasma is assumed to be compensated by volume heat losses such as bremstrahlung. The distribution obtained is far from Maxwellian if the drift velocity is comparable to the thermal velocity of the electrons. Longitudinal oscillations with wave vector in the direction of the field are introduced as a perturbation and their dispersion relation obtained. The stability of the steady state is investigated numerically, and it is found to be unstable for sufficiently high drift velocities, the instability being due to the familiar electron ion two stream interaction. The instability is impeded but not prevented by collisions. We find that the critical drift velocity exceeds that calculated in the collisionless theory by at about 20% in the limit that the electric field and collision frequency approach zero. This difference is attributable to the modification of the velocity distribution function.

ISSN:0031-9171    

DOI:10.1063/1.1762178

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The stability of a weakly ionized plasma column against a screw type perturbation in the presence of an applied axial electric field and a predominantly radial magnetic field—a linear Hall current accelerator—is investigated. The analysis is based on the ion and electron conservation equations and takes into consideration the effects of ionization. It is shown that the observed instability cannot be explained when the axial component of the magnetic field is identically zero even when one takes into consideration steady‐state solutions with both radial and axial dependence. On the other hand, when the axial component of the magnetic field is small, but not zero, the column is unstable in the absence of an axial density gradient to a right‐handed helical perturbation (m= −1). The resulting instability, which is of the Kadomtsev and Nedospasov type, is analyzed using a normal mode analysis. The results are in qualitative agreement with experiment.

ISSN:0031-9171    

DOI:10.1063/1.1762179

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A recombination instability is considered which may arise in a plasma if the temperature dependence of the volume recombination coefficient, &agr;, is sufficiently strong. Two cases are analyzed: (a) a steady‐state plasma produced in a neutral gas by x rays or high energy electrons; and (b) an afterglow plasma.

ISSN:0031-9171    

DOI:10.1063/1.1762180

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A kinetic equation for a plasma with electromagnetic interactions is derived in the shielding approximation. The equation is the analog of the Landau equation and has the same structure as the Landau equation but with a velocity dependent interaction replacing the Coulomb interaction.

ISSN:0031-9171    

DOI:10.1063/1.1762181

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The Lenard‐Balescu kinetic equation for a one‐component inhomogeneous plasma is solved by the Chapman‐Enskog method. The transport coefficients are calculated taking into account collective effects. For most plasmas of interest it is found, to a first approximation, that the value of these coefficients is diminished as compared to that obtained using the Boltzmann‐Landau kinetic equation and cutting off integrals at the Debye distance. The higher approximations are very small compared to the first one.

ISSN:0031-9171    

DOI:10.1063/1.1762182

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The transport coefficients for a binary plasma are calculated starting from the Lenard‐Balescu kinetic equation. The results show that for most plasmas of interest the value of the coefficients are diminished as compared to those obtained from the Boltzmann‐Landau kinetic equation.

ISSN:0031-9171    

DOI:10.1063/1.1762184

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The theory of the skin effect in a plasma is developed for the case in which the relation between current and electric field is not local.

ISSN:0031-9171    

DOI:10.1063/1.1762185

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The experimental observation of the limiting phenomena of ion cyclotron resonance heating in the shallow magnetic beach is described and its explanation by the reflection of the wave is discussed. The temperature‐anisotropic plasma dispersion relation is solved with the aid of an electronic computer. The unexpected singular point which causes the reflection of waves is found in the unstable region of the ion cyclotron wave. The calculated limiting value of the ion temperature due to the wave reflection is given by &bgr;⊥c≈ 4(T∥/T⊥)2, in reasonable agreement with the experiment.

ISSN:0031-9171    

DOI:10.1063/1.1762186

出版商:AIP    

年代:1967

数据来源: AIP