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The basic types of diffusion models available for aerospace air quality analyses are reviewed in terms of meteorological input differences. The NASA/MSFC rocket exhaust effluent diffusion (REED) code is summarized and discussed as a tool for aerospace air quality analyses. The generic approach to a climatological air quality analysis using the NASA/MSFC REED code is considered.
The spatial properties of large aperture exposures of diffuse emission can be used both to investigate spatial variations in the emission and to filter out camera noise in exposures of weak emission sources. Spatial imaging can be accomplished both parallel and perpendicular to dispersion with a resolution of 5-6 arc sec, and a narrow median filter running perpendicular to dispersion across a diffuse image selectively filters out point source features, such as reseaux marks and fast particle hits. Spatial information derived from observations of solar system objects is presented.
The ages of Ar-40/Ar-39 chondrites were computed to be 4.29 to 1.0 Gyr, with degassing times of 0.5 to 1.0 Gyr. The values of the diffusion parameter for Ar in Arrhenius plots show linear relationships which correspond to the degassing of different mineral phases with distinct K/Ca ratios and different average temperatures for Ar release. The experimental values of the diffusion parameter for the high-temperature phase of severely shocked chondrites are 10 to the -7th to 10 to the -5th/s for the shock-heating temperatures in the 950-1200 C range; the inferred reheating temperatures and the fraction of the Ar-40 loss during the reheating event suggest post-shock cooling rates and burial depths of 0.01-0.0001 C/s and 0.5-2m, respectively.
In the present paper, an attempt is made to determine, from the observed intensity profiles for protons and electrons in the region of L smaller than 4, whether population of Saturn's innermost trapped radiation zones from an external source is possible. It is found that if diffusion proceeds in an episodic rather than a steady-state manner (long periods of quiescence interrupted by brief periods of rapid diffusion), the basic features of the observed phase space density profiles are qualitatively reproduced for both the trapped protons and electrons.
The paper analyzes the contributions of QSOs, BL-Lac objects and Seyfert galaxies to the diffuse gamma-ray background within the framework of the Hoyle-Narlikar theory. It is shown that the inconsistency reported in standard theory, namely that the evolutionary function needed to explain the gamma-ray data is very different from the one derived from the optical part of the spectrum, is no longer present. It is also shown that the contribution of a variable gravitational 'constant' to the expression for the diffuse background is the same as that of a density evolution function.
Estimates are obtained of the vertical mass eddy diffusion coefficient of the Venus atmosphere in the region of turbulence near 60 km on the basis of radio scintillations observed during radio occultation by the atmosphere. The structure constant estimated from Pioneer Venus orbit 18 entrance radio occultation measurements is used, under the assumption that the turbulence is generated by wind-shear, to derive a value of 40,000 sq cm/sec for the vertical mass eddy diffusion coefficient, together with an energy dissipation rate of 20 sq cm/sec and a temperature fluctuation dissipation rate of 0.001 K-squared/sec. Results are noted to fall within the range measured for the earth's troposphere, however, indicate that small-scale turbulence is probably the dominant mechanism for vertical transport near the tropopause in the Venus atmosphere.
The Boltzmann-Fokker-Planck equation is solved with the Chapman-Enskog method of analysis for the velocity distribution functions of helium, carbon, nitrogen, and oxygen. The analysis is a perturbation scheme based on the assumption of a collision-dominated gas, and the calculations are carried out to first order. The elements considered are treated as trace constituents in an electron-proton gas. From the resulting distribution functions, diffusion coefficients are computed which are found to be 20-30% less than those obtained by Chapman and Burgers. In addition, it is shown that the return current of cold electrons needed to maintain quasi-neutrality in a plasma with a temperature gradient contributes a term in the thermal diffusion coefficient omitted erroneously in previous works. This added term resolves the longstanding controversy over the discrepancy between the coefficients of Chapman and Burgers, which are seen to be completely equivalent in the light of this analysis. The viscosity coefficient for an electron-proton gas is also computed and found to be 7% less than that obtained by Braginskii.
The results of recent observations of the column densities of chlorine species in diffuse interstellar clouds are inconsistent with the column densities predicted by model calculations. The use of new atomic and molecular data fails to decrease the discrepancy. It is speculated that the exothermic reaction Cl(+) yields HCl(+) + H may not be rapid at the low temperatures prevailing in diffuse interstellar clouds.
The intensity of the diffuse background emission in the far ultraviolet from hot coronal gas present in the plane and halo of the galaxy is calculated. The main emission lines expected are those of C III, IV, N III, IV and Si III, IV at 1909, 1549, 1749, 1487, 1207 and 1398 A respectively. Unless the gas is unusually clumped or has extremely depleted abundances, this source is not of sufficient intensity to influence current broadband measurements of the diffuse continuous ultraviolet background. However, future observations at higher sensitivity and resolution might have to take this effect into account.
It is shown that thermal (Soret) diffusion significantly alters convective mass transport rates and important transition temperatures in highly nonisothermal flow systems involving the transport of 'heavy' species (vapors or particles). Introduction of the Soret transport term is shown to result in mass transfer effects similar to those of 'suction' and a homogeneous chemical 'sink'. It is pointed out that this analogy provides a simple method of correlating and predicting thermal diffusion effects in the abovementioned systems.
An equation is derived to compute the amount of diffuse light reflected by a particulate surface, such as on Mars or an asteroid. The method traces the paths of rays within an ensemble of randomly shaped grains and finds the eventual probability of emission. The amount of diffuse, unpolarized emitted light is obtained in terms of the real index of refraction, the imaginary index, and the average diameter of particles making up the surface. The equation is used to compute the empirical rule for obtaining the planetary albedo from the slope of its polarization curve. Accuracy of the equation, estimated at + or - 4%, seems justified because of quantitative agreement with experimental measures of the empirical rule. It is also shown that the equation can be applied to bubble-enclosing surfaces such as volcanic foams. Results for the indices of the moon, Mars, Io, and Europa are obtained and compared with other data.
The Apollo-Soyuz data and data reported by Cash et al. (1976) have been reanalyzed in terms of both isothermal models and temperature distribution models. In the latter case, a power-law form is assumed for the relation between emission measure and temperature. A new upper limit on diffuse flux in the 20-73 eV band derived from Apollo-Soyuz observations made in the earth's shadow has been incorporated in the calculation. In the considered investigation the results of the new analysis are presented and the implications for the physical properties of the hot component of the interstellar medium are discussed. The analysis of the Berkeley extreme ultraviolet (EUV) diffuse background measurements using either isothermal or power law temperature distribution models for the emitting plasma indicates excellent qualitative agreement with hard X-ray data that suggest the sun to be immersed in a hot plasma that pervades most of space out to approximately 100 pc.
The 6196.0 A diffuse feature is observed in various directions towards moderately and slightly reddened stars at high spectral resolution and signal to noise ratio. The feature is found to be symmetric with no fine structure with an equivalent-width upper unit paralleling that of H2. The feature is as narrow as 0.4 A, although much broader in other stars due to cloud blending in the line of sight, and is absent in all observed stars with E(B-V) less than 0.1, and upper limits more than an order of magnitude below values extrapolated from more reddened stars. Upper limits are determined by multiplying the square root of the number of channels in which the line may lie, and another narrow feature, although highly asymmetric, is observed at 6194.6 A. It is concluded that the results increase the possibility of at least one of the diffuse band carriers being a molecule.
Nine CCN counters of the static diffusion (SDC) type were compared with one another and with continuous flow diffusion (CFD) chambers. The nine SDCs showed a considerable amount of variation, largely attributable to newness and/or lack of prior calibration of some units. The five more consistent instruments agreed quite well, to within at least 20 percent of the NRL mobility analyzer and to within 10 percent at 1 percent supersaturation. There was satisfactory agreement between the more reliable SDC and CFD chambers.
Pratt & Whitney Aircraft is conducting a test program for NASA in order to demonstrate that a controlled-diffusion stator provides low losses at high loadings and Mach numbers. The technology has shown great promise in wind tunnel tests. Details of the design of the controlled diffusion stator vanes and the multiple-circular-arc rotor blades are presented. The stage, including stator and rotor, was designed to be suitable for the first-stage of an advanced multistage, high-pressure compressor.
Using the model of a cell membrane of a spherical surface in which membrane components may diffuse, the rate of localization due to trapping under diffusion control has been estimated by computing an analytical expression for the mean trapping time including the possibilities of a trapping probability less than one and/or the establishment of an equilibrium at the trap boundary.
The rate of solution of a stationary bubble is limited by the diffusion of dissolved gas molecules away from the bubble surface. Diffusion coefficients computed from measured rates of solution give mean values higher than accepted literature values, with standard errors as high as 10% for a single observation. Better accuracy is achieved with sparingly soluble gases, small bubbles, and highly viscous liquids. Accuracy correlates with the Grashof number, indicating that free convection is the major source of error. Accuracy should, therefore, be greatly increased in a gravity-free environment. The fact that the bubble will need no support is an additional important advantage of Spacelab for this measurement.
Two-dimensional transport by linear waves is parameterized by wave velocity and temperature correlations and nonconservative properties of the atmosphere in a residual Eulerian framework. Explicit expressions derived for the eddy tracer flux vector are written in eddy diffusion tensor form, but it is demonstrated that strong coupling of chemistry and temperature through the rate constants, as is the case for ozone, requires additional terms proportional to the mixing ratio and not to its gradient. A variety of limiting cases are discussed. In the residual Eulerian framework the K(yz), K(zy) components are nonzero for a nonconservative atmosphere and/or a reactive tracer. Tracers have common transport coefficients in the limit where their chemistry is negligible in comparison to transience. It is shown that the usual one-dimensional vertical eddy diffusion continuity equation is rigorously valid only when the temperature dependence of the rate constants is negligible and the tracer has strong vertical stratification relative to its horizontal variability.