摘要:

An analysis of the collision frequency of electrons in the terrestrial atmosphere has been made using recent experimental and observational data. Application to collisions of electrons with neutral particles and positive ions shows that the electronic collision frequency is due to neutral particles below the peak of theF1layer and results from positive ions in theF2layer.

ISSN:0031-9171    

DOI:10.1063/1.1705916

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The relaxation of electrons to equilibrium in the absence of an external field is discussed for a slightly ionized gas in which elastic collisions predominate. The gas consists of electrons and neutral molecules having a Maxwellian interaction. Spatial diffusion is neglected as well as electron‐electron interaction. The change of the electronic distribution function from a simple nonequilibrium distribution to a Maxwellian distribution is followed in time. Electron attachment to neutral molecules is briefly considered.

ISSN:0031-9171    

DOI:10.1063/1.1705898

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Of prime concern in plasma investigations is the coupling of a bounded plasma with external electromagnetic fields. In the present paper the properties of the normal modes of a cold plasma slab, and cylinder, situated in a strong magnetic field are derived, and then used to discuss the transmission and reflection of radiation, the scattering by a plasma cylinder, the response to driving sources in the vicinity of the plasma, and the radiation due to plasma oscillations.

ISSN:0031-9171    

DOI:10.1063/1.1705899

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The theory of sperical and cylindrical probes immersed in plasmas of such low density that collisions can be neglected is formulated. The appropriate Boltzmann equation is solved, yielding the particle density and flux as functionals of the electrostatic potential, the situation in the body of the plasma, and the properties of the probe. This information when inserted in Poisson's equation serves to determine the potential, and hence the probe characteristic. Noa prioriseparation into sheath and plasma regions is required. Though amenable to a determination of the full probe characteristic, the method is applied in detail and numerical results are presented only for the collection of monoenergetic ions, for the case of negligible electron current. These results indicate that the potential is not so insensitive to ion energy as has been believed, and that if the probe radius is sufficiently small, there enters the possibility of a class of ions which are trapped near the probe in troughs of the effective radial potential energy. The population of these trapped ions is determined by collisions, however infrequent. It is difficult to calculate, and conceivably can have a marked effect on the local potential.

ISSN:0031-9171    

DOI:10.1063/1.1705900

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Some exact, closed‐form solutions of the Navier‐Stokes equations for incompressible flow and of the hydromagnetic equations for high‐conductivity, incompressible flow are presented. They can be considered to be generalizations of Taylor's solutions. The solutions are two dimensional and cellular containing a single‐space Fourier component; the spatial behavior is chosen in such a way that the nonlinear inertial term and the pressure term cancel one another, leaving a linear system to be solved. The time behavior of the solutions is quite general. The solutions to the hydromagnetic equations are such that the velocity and the magnetic fields are parallel and decoupled. The velocity behaves as it does in the purely mechanical case while the magnetic field simply decays in time; there is no source term for it in the present treatment.

ISSN:0031-9171    

DOI:10.1063/1.1705901

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

The inhibition of instability of a viscous fluid contained in a circular cylinder and heated from below by an electric current is investigated. Previous results indicate that, for a thermally nonconducting wall, the critical Rayleigh number is 452.1 for symmetric convection, and 67.9 for the first (and critical) mode of unsymmetric convection. It has been found in this investigation that unsymmetric convections can be delayed or completely inhibited by an electric current, whereas symmetric convection is not at all affected. This indicates a very interesting physical situation at Rayleigh number 452.1, for an electric current just strong enough to inhibit unsymmetric convection. If the current is slightly increased, only symmetric motion will occur. If it is slightly decreased, unsymmetric convection, being more unstable, will prevail. Thus the physically significant solution of a differential system may have a sudden change of behavior at certain critical values of its parameters.

ISSN:0031-9171    

DOI:10.1063/1.1705902

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Experimental studies have been made of the onset of natural convection in liquids subjected to heating from below while insulated above. The temperature gradient necessary for convection to start was measured with a thermopile immersed in the liquid. When the liquids were not rotating, it was found that the temperature difference between the top and bottom surfaces required to initiate convection can be related with the heat input by the formulaRa=90.7 (Ra·Nu)0.394,Ra>1700,where Ra is the Rayleigh number, and Nu is the Nusselt number, both specially defined for the transient case. Mercury and silicone oil were used in the experiments without rotation. It was found in experiments with mercury, that in the range of Taylor numbers covered, the presence of spin increased the temperature difference required to initiate convection. The Rayleigh number necessary for the onset of fluid motion in spinning mercury is plotted as a function of the Taylor number for several values of the heat flux.

ISSN:0031-9171    

DOI:10.1063/1.1705903

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Similarity solutions are given for the energy spectrum and transfer function in the initial period of decay for a range of values of the Reynolds number using the transfer theory suggested by Kova´sznay. Because of the simple form of the theory, the solution can be obtained in closed form for all values of the Reynolds number, and this exact solution is useful for analytical purposes. To obtain detailed results, however, it is more convenient to employ numberical methods. It is found, for example, that the skewness factorSof −∂u1/∂x1varies only between 3.93KKforR&lgr;= 0 and 2.86KKforR&lgr;= ∞, whereKKis the arbitrary constant that occurs in the theory. A comparison between the present results and those obtained by using Heisenberg's transfer formula is also made. Some results for the transfer function in the final period of decay are also given.

ISSN:0031-9171    

DOI:10.1063/1.1705904

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

For the diatomic molecule AB in thermal and chemical equilibrium with its dissociated atoms, the pressure, density, specific entropy, and specific enthalpy are written as functions of the temperature and the fractional dissociation, with the approximations that the rotation is fully excited and there is no electronic excitation. These approximations are very good for many molecules over a large range of the variables. Atoms A and B can be either identical or distinct provided there is no excess of one atom over the other. For molecules composed of the isotopes of hydrogen, because of their large vibrational energies, it is possible to have considerable dissociation without vibration being important. If vibration is neglected, then the thermodynamic variables (written in dimensionless form) are related by equations which do not involve any properties of the species under consideration. Curves of constant pressure, density, specific entropy, and specific enthalpy are presented in the temperature‐dissociation plane. The errors introduced by neglecting vibration are proportional to exp (−TV/T), whereTVis the vibrational temperature.

ISSN:0031-9171    

DOI:10.1063/1.1705905

出版商:AIP    

年代:1959

数据来源: AIP

摘要:

Shock‐tube and discharge techniques make it possible to generate in the laboratory significant volumes of dissociated and/or ionized gases. This paper describes some studies of the optical index of refraction &mgr; of dissociated diatomic gases. The physical interpretation of specific refractivityK= (&mgr; − 1)/&rgr; is discussed and related to polarizability, and various methods of computing such quantities are reviewed briefly. Shock‐tube experiments are described in which optical interferometry has been utilized to measure the polarizability of atomic oxygen and nitrogen with the result&agr;¯(O I)=0.77±0.06 A3and&agr;¯(N I)=1.13±0.06 A3. The use of optical interferometry for determination of gas density has been justified for experiments involving air at temperatures to at least 5000°K.

ISSN:0031-9171    

DOI:10.1063/1.1705906

出版商:AIP    

年代:1959

数据来源: AIP