摘要:

The self‐consistent equilibrium configurations available to low‐density (q= &ohgr;p2/&ohgr;c2≪ 1) toroidal electron clouds under the influence of an external magnetic field and the electric fields due to space and image charges are discussed. The equilibria are dynamic rather than static, but steady. ▿B, centrifugal, and other drifts are shown to be unimportant, in contrast to the situation in toroidal neutral plasmas. Typical equilibria are shown in detail, to zero order inq. The construction of equilibria accurate to orderqis shown to be possible but is not carried out in detail. Questions relating to the stability of these equilibria are not treated.

ISSN:0031-9171    

DOI:10.1063/1.1761966

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The coupling of energy among electron‐acoustic, ion‐acoustic, and transverse electromagnetic waves at a density discontinuity in a two‐fluid fully ionized plasma is studied by means of the plane wave solutions of the linearized equations of hydrodynamics and Maxwell's equations. An expression for energy conservation in a two‐fluid plasma is discussed and applied to energy coupling among the three allowed modes. Numerical results for all types of wave coupling illustrate the influence of the plasma parameters on the efficiency of energy conversion.

ISSN:0031-9171    

DOI:10.1063/1.1761967

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A perturbation scheme is devised for investigating the periodic solutions of a nonlinear, second‐order, ordinary differential equation with an additional small nonlinear term. It is assumed that when the additional term vanishes the solution to the remaining zeroth‐order nonlinear equation is known. When this is the case, explicit expressions for the first‐order solution and the first‐order correction to the dispersion relation are given in terms of the known zeroth‐order solution.

ISSN:0031-9171    

DOI:10.1063/1.1761969

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The problem of calculating the amount of energy which can be stored in a plasma near the upper hybrid resonance is treated by considering a macroscopic plasma model in which all nonlinear terms are maintained. For frequencies sufficiently close to the hybrid frequency, and for low temperatures, application of the traveling wave hypothesis reduces the macroscopic equations to an ordinary nonlinear differential equation with an additional small nonlinear term. The solution of this equation, by the perturbation procedure described in Pt. I, indicates that nonlinear effects (overtaking and trapping) become more important at lower energy levels as the frequency approaches the hybrid frequency. Explicit expressions are given for the maximum allowable stored energy at hybrid frequency in both a cold and warm plasma.

ISSN:0031-9171    

DOI:10.1063/1.1761970

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The effective electron and ion diffusion coefficients have been measured in magnetic field configurations with positive, zero, and negative gradients of the magnetic inductionBzacross the field. The radial density profiles are approximately the same for a mirror configuration ∂Bz/∂r< 0 and a uniform field ∂Bz/∂r= 0. The measured electron diffusion coefficient is by orders of magnitude larger than the collisional one and shows the 1/Bdependence of the Bohm‐type diffusion process,D⊥−=C kTe/B. The factorChas been determined toC∼ 10−2. The noise level diminishes and the density profiles become steeper with increasing positive gradients, ∂Bz/∂r> 0, thus showing reduced plasma diffusion. A sharp drop of the electron saturation current to the probe indicates that the anomalous diffusion of the electrons is strongly reduced in certain regions where the radial electric field is weak. The stabilizing effect of an average minimum‐Bfield has been confirmed experimentally.

ISSN:0031-9171    

DOI:10.1063/1.1761971

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

A general class of solutions is obtained for fully ionized plasmas which admit transverse electromagnetic waves with constant phase velocity. The solutions self‐consistently satisfy Maxwell's equations and Vlasov's equations for both ions and electrons. It is shown, for plasmas admitting such waves, that the mean velocity in the direction of the propagating wave is equal to the wave speed when the plasma is in a stationary state and is different from the wave speed for nonstationary states. A specific set of ion and electron distribution functions is presented which admit monochromatic waves. The associated moments and compatibility relations are calculated.

ISSN:0031-9171    

DOI:10.1063/1.1761972

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

An exact, self‐consistent solution of the system of Vlasov's plus Maxwell's equations is derived, describing a warm stationary plasma in a uniformly sheared magnetic field. It is found that there is no upper limit for the rate of shear; that is, the distance over which the direction of the magnetic field rotates of an angle 2&pgr; can be as small as desired; in particular this distance can be smaller than the ion or even the electron Larmor radius. Within the assumed model, for any value of plasma density, magnetic field strength and rate of sheara prioriassigned, there exists a one‐parameter family of solutions, differing from each other essentially for the fraction of the total current that goes into ion or electron current, respectively. The two currents can also flow in opposite directions, thus subtracting from each other in producing the net total current; in this case, however, they cannot separately exceed certain limiting values, set by the requirement of integrability for the distribution functions.

ISSN:0031-9171    

DOI:10.1063/1.1761973

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

For a plasma with finite cross section of the sort which occurs typically in laboratory plasma waves experiments, in a constant magnetic field, the Landau damping (or growth) is obtained by a perturbation procedure in terms of the plasma velocity distribution function and potential and density profiles. The result is applied to the damping associated with the upper and lower branches of the dispersion curve for longitudinal electron plasma waves in the case of a Maxwellian velocity distribution in slab and cylindrical geometries. Application is also made to the growth rates resulting from a low‐density electron beam with radially dependent energy superposed on a Maxwellian.

ISSN:0031-9171    

DOI:10.1063/1.1761974

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

Low‐frequency electron density fluctuations of a bounded homogeneous plasma are determined at large wavelengths. It is shown that, when the wavelengths are large, the frequency spectrum of fluctuation is determined by the mean square displacement of an electron in a time intervalt, ⟨&Dgr;(t)2⟩. Using a Brownian motion model for ⟨&Dgr;(t)2⟩ which is exact at larget(as well as at smallt), the frequency spectrum can then be evaluated by the method of steepest descents. The resulting spectrum is exact at zero frequency and provides a method for local measurements of diffusion cofficients by light scattering or direct probe measurement techniques. The results are valid regardless of the number of particles in a Debye sphere or of the extent of ionization.

ISSN:0031-9171    

DOI:10.1063/1.1761975

出版商:AIP    

年代:1967

数据来源: AIP

摘要:

The linearized response of a collisionless plasma model to external applied fields is calculated and examined with respect to its causal behavior. It is found that causality is not automatically fulfilled but must be imposed. The Titchmarsh theorem of complex analysis is used as a guide in imposing causality. Alternatively, it is shown that causality can be achieved by adding a damping term to the model and allowing the damping rate, which this term introduces, approach zero.

ISSN:0031-9171    

DOI:10.1063/1.1761976

出版商:AIP    

年代:1967

数据来源: AIP