摘要:

The asymptotic or self‐similar behavior of the one‐dimensional two‐stream instability previously observed in numerical simulations is investigated theoretically. The main result, the relation&ngr;d = &ngr;e, implies a principle of maximum dissipation. On the microscopic level it is shown that the quasilinear solution is inconsistent with&ngr;d = &ngr;, and the assumption of an adiabatically growing Bernstein‐Greene‐Kruskal wave cannot explain the observed similarity law. It is proposed that the observed behavior is due to the instability of a Bernstein‐Greene‐Kruskal wave. Suitably chosen simulation computations are performed to demonstrate this concept.

ISSN:0031-9171    

DOI:10.1063/1.1694441

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A detailed analysis is given of the development of the electrostatic turbulence excited by a cross‐field current in a high density(&ohgr;p e ≫ &OHgr;e )collisionless plasma, as obtained from one‐ and two‐dimensional computer simulations. The drift velocity required for instability is found to be only slightly smaller than the critical drift for the unmagnetic two‐stream instability in contrast to the electron cyclotron drift instability. In one dimension the system remains self‐similar in the turbulent phase,< E˜2 > /8&pgr;nTe ≃ const, while the electron thermal velocity and the effective collision frequency increase linearly with time,&ngr;* ∝ &OHgr;et, in agreement with the theory of coherent trapped‐electron heating by Forslund, Morse, and Nielson. The switch‐off drift velocity, however, is&ngr;d ≈ 2cs, and hence the thickness of a magnetic sheath would be&Dgr; ∼ c/&ohgr;piinstead of&Dgr; ∼ c/&OHgr;e. In two dimensions two projections are investigated, thej‐Bplane and the plane perpendicular toB, the latter being the more relevant. The heating is much less efficient than in one dimension,&ngr; * ≲ 5 × 10−3 &ohgr;pe. It is found that&ngr;* ∝ ⟨E˜2⟩/8&pgr;nT, indicating stochastic dissipation. The gross features of the two‐dimensional behavior correspond to the picture of ion‐sound instability with electron runaway prevented by gyration.

ISSN:0031-9171    

DOI:10.1063/1.1694442

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An unneutralized rigidly rotating electron beam is absolutely stable if the distribution function is a monotonically decreasing function ofH0 −&ohgr;LLzand if(&rgr;B&ohgr;l/c) < 1, whereHOandLzare the single‐particle energy and canonical angular momentum,&ohgr;Lis the angular velocity, and&rgr;Bis the radius of an enclosing infinitely conducting cylindrical wall.

ISSN:0031-9171    

DOI:10.1063/1.1694443

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A short pulse of relativistic electrons propagating along a preionized channel of high conductivity may assume a hollow equilibrium profile as a result of induced plasma currents. In this configuration the pulse is neutrally stable with respect to lateral expulsion from the channel by the induced currents. The properties of a thin hollow shell equilibrium are derived.

ISSN:0031-9171    

DOI:10.1063/1.1694444

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

It is shown that limitations on collisionless electron thermal conduction place a lower limit on the range of energies of electrons in the surface of target plasmas which are heated by incident electromagnetic radiation, and that in cases of contemporary experimental interest these energies can be hundreds of keV. It is then shown that these high‐energy electrons can cause a much faster expansion of plasma from the heated surface than would be predicted by a single fluid theory. Numerical simulations demonstrate both effects.

ISSN:0031-9171    

DOI:10.1063/1.1694445

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Parametric interactions among plasma waves propagating along an applied dc magnetic field are examined. The driving mechanism consists of either an ac electric field impressed transversely to the applied magnetic field, or bunches of particles injected with preferential phase. The physical system is composed of a (possibly infinite) number of cold beams. The equations are linearized with the effect of the induced first‐order magnetic field included throughout. Six absolute instabilities are found to result from the coupling between two electronic modes of a cold plasma and three more result from a coupling between an electronic mode and the ion cyclotron branch. The extension to temperate plasmas is indicated. The instabilities become important in systems with high transverse velocity&ngr;0⊥, since the growth rates calculated from coupling of modes go as&ngr;0⊥/c or &ngr;0⊥2/c2. These interactions may find application to fusion and microwave devices. In particular, those with the ions may be useful as energy transfer mechanisms.

ISSN:0031-9171    

DOI:10.1063/1.1694446

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

An adiabatic theory of the energy exchange between magnetically confined charged particles and a traveling electrostatic wave with slowly varying phase speed and amplitude is presented. The results are applied to a basic assessment of the usefulness of traveling‐wave techniques for efficient energy recovery from energetic plasma streams. Severe constraints on the energy conversion efficiency attainable by this approach are indicated by the model.

ISSN:0031-9171    

DOI:10.1063/1.1694447

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

Experimental values of the ratio of Reynolds shear stress to turbulence kinetic energy for a compressible boundary layer are presented. This ratio, for nonequilibrium compressible flows, is shown to be near the value of 0.15 obtained in equilibrium, incompressible flows.

ISSN:0031-9171    

DOI:10.1063/1.1694448

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

A closed form solution of the von Ka´rma´n integral equation that describes the turbulent cascade is presented for a universal equilibrium spectrum under the specific assumption that the energy transfer from the macro to the micro components is due to the same mechanical process.

ISSN:0031-9171    

DOI:10.1063/1.1694449

出版商:AIP    

年代:1973

数据来源: AIP

摘要:

The rarefied gas flow in a circular tube whose wall is nonuniform in temperature is analyzed using the Maxwell moment method, with special reference to thermal creep. The results obtained are in fair agreement with both Sone and Yamamoto's and the calculations worked out at the low Knudsen number by the elementary kinetic theory of gases.

ISSN:0031-9171    

DOI:10.1063/1.1694450

出版商:AIP    

年代:1973

数据来源: AIP