摘要:

A modified microwave cavity technique was used to measure the decay rates of electron densities in air afterglows. Measurements of low‐duty cycle or single discharges which were not affected by the discharge products of preceding events were obtained by monitoring the shifts of the resonant frequencies. Results of measurements in late afterglows show that one loss mechanism can be described by an effective ambipolar diffusion coefficient representing participation of two positive ions in the process; the ions being most likely O2+and NO+. The other loss mechanism is due to two‐body attachment of electrons, the likely attaching specie being NO2. The measurements on two differentx‐band cavities in the pressure range 0.1‐10.0 Torr for ambipolar diffusion yielded:Da,eff p = 122 ± 18cm2/secTorr and for attachment:hav1 = (4.9 ± 0.15) × 103sec−1Torr−1.

ISSN:0031-9171    

DOI:10.1063/1.1692717

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Properties of electrons near absorbing and emitting surfaces are studied for weakly ionized plasmas by analyzing the Boltzmann equation governing the electrons. For simplicity, it is assumed that the electric field intensity is given apriori. It is shown that there exists a “nonequilibrium absorption layer,” near the surface, wherein the kinetic distribution of electrons is completely out of equilibrium for all values of the mean free path, when the surface is highly absorbent with small or no electron emission. This layer is responsible for the large electron temperature jump at the surface, and it governs the electron temperature profile through the continuum as well as the rarefied plasmas. From the analysis it is found that the simple surface boundary condition for the continuum electron energy equation previously employed by the present author is correct when there is no surface emission. A similar simple surface boundary condition is deduced for surfaces with given finite emission rates.

ISSN:0031-9171    

DOI:10.1063/1.1692718

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The source of the anomalous resistivity that broadens shock fronts in a near‐collisionless plasma is attributed to the drift‐wave instability driven by the strong electron temperature gradients in the front. Whistler‐type waves propagating through the electrons in the plane of the shock front are treated by the fluid equations, with the ions kept unperturbed. The fastest growing unstable waves are found to propagate normal to the magnetic field, for which case the whistlers degenerate to convected waves. Resistivity is introduced such that it exactly cancels the growth rate due to the gradients, and the calculation is made self‐consistent by using this resistivity to deduce the magnitude of the gradient. The main results are simple formulas for the anomalous collision frequency and the resistive shock thickness&lgr;&eegr;. It is found that&lgr;&eegr; ≃ (Te2/mev1)1/2 (c/&ohgr;pe), where the subscripts 1 and 2 refer to conditions upstream and downstream of the shock, andvis the component of plasma velocity normal to the stationary shock. This result is found to be in reasonable agreement with the few available experimental results.

ISSN:0031-9171    

DOI:10.1063/1.1692719

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The propagation properties of coherent magnetohydrodynamic waves in the presence of plasma density fluctuations are investigated. A perturbation technique borrowed from quantum field theory (renormalization procedure) is used to solve the stochastic wave equation. Effective propagation and attenuation constants are derived for propagation of plane coherent magnetohydrodynamic waves. It is found that, in general, the phase velocity will be less than the Alfve´n velocity and there will be attenuation (or damping) of the waves due to the random mixing of phase.

ISSN:0031-9171    

DOI:10.1063/1.1692720

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

A one‐parameter family of exact hydromagnetic‐equilibrium solutions is found describing a plasma of finite pressure(0 ≤ &bgr; ≤ 1)confined by a force‐free magnetic field contained within a perfectly conducting sphere.

ISSN:0031-9171    

DOI:10.1063/1.1692721

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

Temporal behavior of some physical quantities is investigated for the system of electron plasma and injected beam with fixed velocity distributions. The fluctuation of the electric field with the critical wavenumberk0(defined by&ggr;ko = 0) grows secularly; the velocity diffusion coefficient forv0(defined by&ohgr;ko = k0·v0) grows in proportion to logt; the rate of energy loss by the beam approaches the enhanced value ast−1/2.

ISSN:0031-9171    

DOI:10.1063/1.1692722

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The effect of finite temperature on the width of a magnetic solitary wave is calculated by expanding the Vlasov equation. The calculation is valid when this width exceeds the ion gyroradius but is less than the electron gyroradius.

ISSN:0031-9171    

DOI:10.1063/1.1692723

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The transfer of energy between an electron beam and longitudinal waves in a collisionless plasma has been studied. The quasilinear theory, with the inclusion of the spontaneous emission of wave energy, is used. Numerical solutions of the resulting equations are obtained and compared with those of the quasilinear theory.

ISSN:0031-9171    

DOI:10.1063/1.1692724

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

The theory of the guiding center plasma is extended to include previously neglected terms proportional to the particle mass‐to‐charge ratiom/e. To do this it is necessary to obtain a correspondingly accurate solution of the single charged particle equation of motion. Then, one may define a conservation equation for the time average particle motion or, equivalently, for guiding centers. This equation is combined with a macroscopic momentum equation through the use of a generalized Ohm's law. Adding Maxwell's equations, the result is a self‐consistent set of higher‐order equations describing the behavior of the guiding center plasma. These equations are then linearized in small perturbations about a uniform equilibrium configuration to obtain stability criteria. The results show that these criteria are the same as those of the lowest‐order system.

ISSN:0031-9171    

DOI:10.1063/1.1692725

出版商:AIP    

年代:1969

数据来源: AIP

摘要:

It is shown that the symmetry properties of a time‐independent solution of the set of Vlasov's and Maxwell's equations naturally leads to constants of the motion of the linearized equations. The constants corresponding to invariance under translations in time and to invariance under spatial translations and rotations are explicitly obtained.

ISSN:0031-9171    

DOI:10.1063/1.1692726

出版商:AIP    

年代:1969

数据来源: AIP