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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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NASA NTRS1979

Minimum-flux coronal models for hydrogen and helium white dwarf atmospheres

Families of zero-mass-loss coronal models based on the minimum-flux prescription of Hearn (1975), in which bound-bound, bound-free, and free-free radiative processes with their differing emissivity vs. temperature laws are included, have been computed. These models are applied to the case of white-dwarf envelopes of pure hydrogen or helium, and the results are expressed as relationships between the required total energy flux, the coronal base pressure, and its temperature. The soft X-ray detection of Sirius by the ANS group is discussed. If all the X-ray flux is ascribed to a minimum-flux hydrogen corona surrounding the white dwarf Sirius B, it must have a temperature of 1.6 + or -0.3 million K and a base pressure of 110,000 + or - 40,000 dyne/sq cm. The surface energy flux needed to heat such a corona is (9 + or - 5) x 10 to the 10th erg/sq cm per sec.

Lampton, M.↗
NASA NTRS1980

Variability of the solar flux in the far ultraviolet 1175-2100 A

An attempt is made to correlate available observations within the framework of a simple two-component model of the full-disk flux which divides the solar surface into quiet and active areas with a constant average contrast factor for the intensity at a particular wavelength. The expected range of variability over the solar cycle of the far UV flux is examined within the 1175-2100 A wavelength range. Two possible indices of solar variability, the calcium plage index and the Zurich sunspot number, are investigated as guides to the fraction of disk covered by active regions and the possible resulting flux variability. In addition, contrast factors I(plage)/I(quiet region) are determined for various lines and continua, and the fraction of the disk covered by plages at various times is estimated. Results are in good agreement with the L-alpha fluxes of Vidal-Madjar (1975) and the broadband observations by Hinteregger (1979), but disagree with the flux variability reported by Heath and Thekaekara (1977) over the 1700-3000 A range.

Cook, J. W.↗
NASA NTRS1982

Orienting and Applying Flux to Solar Cells

Solar cells are oriented and fluxed automatically at first work station along solar-array assembly line. In under 2 seconds rotary drive rotates cell into proper position for applying solder flux to bus pad on collector side. When contact bus pad is in correct position, capstan drive is disengaged, and vacuum holddown beneath cell is turned on. Flux system lowers and applies preset amount of solder flux to bus pad. Two interconnect tabs are soldered to fluxed areas.

Feder, H.↗
NASA NTRS1981

Latitudinal anisotropy of the solar far ultraviolet flux - Effect on the Lyman alpha sky background

An estimate is given for the anisotropy of the solar full disk flux in the far ultraviolet, as it would be observed for lines of sight within and above the ecliptic plane through the predominant influence of plages at low heliocentric latitudes. The flux anisotropy for Lyman alpha, at a level of solar activity with a sunspot number of roughly 160, is approximately 0.88 for the integrated flux over the Lyman alpha profile and 0.83 for the flux at line center. The effect of this Lyman alpha flux anisotropy on the Lyman alpha sky background intensity, resonantly backscattered from the local interstellar medium that is streaming through the solar system, is examined. It is concluded that the solar Lyman alpha anisotropy should be included in models of the interplanetary background during periods of moderate to high solar activity.

Cook, J. W.↗
NASA NTRS1980

On the constancy of solar particle fluxes from track, thermoluminescence and solar wind measurements in lunar rocks

Evidence contained within lunar rocks concerning possible variations in solar activity over the last 1 to 2 million years is reviewed. The effects of solar wind particles, which are implanted at shallow depths, solar flare protons, which produce thermoluminescence as well as stable and radionuclides, and solar flare heavy nuclei, which produce tracks, are considered, and the quality and limitations of nuclear tracks measurements as indicators of solar flare flux histories are discussed. Methods used for the determination of the solar flare track production rate, which must be known in order to measure lunar rock surface exposure times, are compared, and it is concluded that most of the evidence favors the rate obtained by Blanford et al. (1975). Information on the constancy of the solar flare particle flux obtained by comparison of the effects of different surface phenomena with solar particle effects is then illustrated for the cases of comparisons between solar flare tracks and microcrater densities, solar flare particle fluxes measured over different periods, and comparisons of the solar flare track production rate with the solar wind flux and microcratering rate. It is noted that these studies provide no evidence for a change in solar particle flux by more than a factor of two over the last 10,000 to 1 million years, or for a change in the solar flare Fe/H ratio in the last 2 million years.

Zinner, E.↗
NASA NTRS1981

Heat flux estimates over vegetation derived using radiometric surface temperatures and a boundary layer model in comparison with sodar-derived values

An attempt was made to validate a method that uses radiometric surface temperatures and a boundary layer model to estimate surface energy budgets and characteristics. Surface temperatures from a hand-held radiometer and sodar data were collected simultaneously on seven days between mid-July and mid-October 1980. The comparison of the RDMS and sodar heat fluxes proved disappointing. Free convection conditions, required to produce sodar-derived heat fluxes, were inhibited by a terrain-induced low level inversion. Only three out of seven cases produced meaningful sodar heat fluxes. Of those three cases, one had good agreement and the other two had sodar heat fluxes 15 to 45 w/sq m lower than the RDMS values. Since the RDMS method is relatively untested, it was impossible to conclusively determine its validity from the results. There was evidence that the true heat flux was not underestimated by the RDMS, so it could be concluded that the Bowen ratios over well-watered vegetation were likely to be quite small.

Cooper, J. N.↗
NASA NTRS1981

Factors governing the ratio of inward to outward diffusing flux of satellite ions

The sensitivity of the flux ratio to the uncertainties in the boundary conditions and diffusion coefficient is analyzed. The principal result is that if the diffusion is driven externally, for example, by winds in Jupiter's ionosphere, the inward flux exceeds or is of the same order of magnitude as the outward flux. On the other hand, if the diffusion is driven locally by the centrifugal interchange instability, as suggested by one interpretation of Voyager plasma data, the outward flux can be one or two orders of magnitude greater than the inward flux. Fits to the Voyager in situ plasma torus data obtained through solutions to the transport equations appropriate to wind driven and centrifugally driven diffusion are compared.

Richardson, J. D.↗
NASA NTRS1981

Bound oscillations on thin magnetic flux tubes - Convective instability and umbral oscillations

The possibility that 'tube waves' can be trapped on slender solar magnetic flux tubes is investigated. For rigid isothermal flux tubes, it is found that the flux tube geometry can by itself lead to waves which are trapped on the part of the tube that expands with height. Some geometries lead to trapped modes with eigenperiods near 180 s, if parameters appropriate to sunspot umbrae are chosen. It is possible that the umbral oscillations are a manifestation of such trapped waves, if sunspot umbrae consist of an assembly of slender flux tubes, as in the spaghetti model of Parker (1979). For flux tubes which have a constant ratio of Alfven speed to sound speed, it is found that it is primarily the variation of temperature with height which determines whether trapped waves can exist. Certain temperature profiles lead to disturbances for which omega squared is less than zero, corresponding to convective instability or Rayleigh-Taylor instability.

Hollweg, J. V.↗
NASA NTRS1982

Properties of the Eliassen-Palm flux for planetary scale motions

In an investigation of the properties of the quasi-geostrophic Eliassen-Palm (EP) flux for planetary-scale motions, particular attention is given to the relation between the EP flux divergence and the meridional flux of eddy potential vorticity, and the relations between the EP flux, group velocity, and the zonal mean refractive index in the Wentzel-Kramers-Brillouin-Jeffreys limit. This latter diagnostic has appeared in a number of different forms as that quantity whose gradient determines the refraction of group velocity paths or EP flux trajectories. The question is considered which, if any, of these forms holds for planetary scale motions. In this investigation, a planetary-scale motion is formally defined to be one for which Burger's (1958) quasigeostrophic theory is appropriate.

Palmer, T. N.↗
NASA NTRS1982

Short-term fluctuations in the eddy heat flux and baroclinic stability of the atmosphere

National Meteorological Center data from midlatitudes for three Januaries is used in calculating time series of the zonal mean meridional eddy heat flux and the zonal mean baroclinic stability, as measured by the difference between the zonal wind shear and the critical value of the shear in two-level models. Time-lagged correlations between the two series reveal a highly significant negative correlation for short time lags, peaking at approximately -0.4 when the stability parameter lags one half day behind the eddy flux. They also reveal that strongly unstable conditions are not followed by significant increases in the eddy flux. These results are seen as indicating that the synoptic variations of the zonal mean eddy flux are not closely related to the degree of baroclinic instability of the zonal mean flow. The autocorrelation of the eddy flux is then compared with those expected for autoregressive processes. A Bayesian information criterion suggests that the behavior is represented best by a damped oscillation, with a damping time of 0.8 day and a period of five days.

Stone, P. H.↗
NASA NTRS1982

The magnetic flux in the quiet sun network

Direct magnetic measurements are used to confirm that the Ca II K line emission from the quiet sun network does not vary with the 11 year cycle (White and Livingston, 1981). As the K emission intensity is correlated with magnetic field strength, magnetic flux measurements are valid for comparison. Data were taken from the full-disk Mount Wilson daily magnetograms, and the aperture was decreased from 17.5 to 12.5 during the interval 1970 through 1980. Measurements are restricted to the latitude zones centered on + or - 1.7 degrees. The mean total flux in the + or - 15.3 degree zones increased by a factor of 10 between activity minimum and maximum, and the quiet sun flux shows no variation, thus confirming White and Livingston's (1981) result. In order for the amplitude of the quiet sun magnetic flux to remain constant, a balance between increasing and decreasing factors must exist, and the primary factor in this balance is the rate of destruction of the quiet sun flux.

Labonte, B. J.↗
NASA NTRS1982

Satellite estimates of ocean-air heat fluxes during cold air outbreaks

A method for estimating the heat and moisture fluxes of coastal waters using the cloud free path, the sea surface temperature, and the saturation water vapor mixing ratio is presented. Generalized nomograms for the surface sensible and latent heat fluxes are developed using the Stage and Businger (1981) mixed-layer model. The fluxes are found to be slightly dependent on wind speed. The results are found to be applicable to any path within the cloud-free region, with heat fluxes obtainable by multiplication of the mean heating by the mean wind speed in the boundary layer. Higher stability causes lowered heating. It is shown that the latent heat flux is linear. Applications of the method to lake-effect snowstorms and for verification of boundary-layer models are indicated.

Chou, S.-H.↗
NASA NTRS1983

Identification of radio emission from the Io flux tube

The identification of a specific Jovian decametric emission with the particular flux tube near the orbit of Io giving rise to it would substantially improve theoretical understandings of the relation of the Io flux tubes with the arc-like structures seen on time vs. frequency plots of decametric emissions observed by the Voyager spacecraft. The present paper shows how the instantaneous Io flux tube may be identified with particular emission features. It is demonstrated that the emissions designated Io caused emission (ICE) may be interpreted as representing sections of arc structures emitted by the interaction of Io with successive flux tubes. The model is capable of accounting for the change of displacement angle of the ICE structures as the sub-observed Jovian longitude changes. The identification permits the mapping of emissions onto the causative flux tubes for Jovian longitudes from 240 to 360 deg.

Riddle, A. C.↗
NASA NTRS1983

Absence of equilibrium among close-packed twisted flux tubes

The lack of equilibrium in twisted, close-packed flux tubes is demonstrated in terms of a topology of the transverse field and the necessity of defining restricted solutions for an arbitrary function in the equilibrium equation. It is shown that nearly all combinations of flux connections and functional forms have no mutual equilibrium and that the flux connections in nature are formed by footprint convection at an origin. The most close-packed twisted flux tubes are subject to dynamical nonequilibrium, with the transverse flux connections being reduced through neutral point rapid reconnection. The precise solutions which can be obtained through functional forms in the equilibrium equation do not have an analog in the real world.

Parker, E. N.↗
NASA NTRS1984

Evolution of Solar Magnetic Flux

The appearance of solar magnetic flux is discussed; both the mechanisms and phenomena associated with flux emergence are considered. The dynamics of solar surface magnetic flux are addressed, including both the transport and structure of magnetic-flux-carrying elements as seen in the chromosphere and corona. The disappearance of magnetic flux from the surface of the Sun is also discussed. Standard solar models representing generally accepted views are considered along with observations which seem to fall outside the scope of these models.

Source record↗
NASA NTRS1982

Effect of electron flux on radiation damage in GaAs solar cells

The objective of this work was to evaluate the effect of electron flux and temperature on radiation damage in GaAs solar cells. The defect levels and the power ratio of the GaAs solar cells under various irradiation conditions are compared. In a 200 C continuous annealing experiment, the GaAs solar cells which were irradiated at a flux of 2 x 10 to the 9th e/sq cm s suffered less power degradation than the cells which were irradiated at the same temperature at a higher flux of 4 x 10 to the 10th e/sq cm s. After the continuous annealing experiment, a single-step post annealing at 200 C was performed for 40 hr on these irradiated cells. An additional improvement in power recovery was observed only on those cells irradiated at the high flux of 4 x 10 to the 10th e/sq cm s. DLTS data indicate that the defect density decreases with lower electron flux. Both of these observations strongly suggest that the continuous annealing in GaAs cells can be effective at temperatures as low as 150 C, or even less in a space environment such as geosynchronous orbit.

Loo, R. Y.↗
NASA NTRS1984

Propagation of axisymmetric disturbances on a twisted magnetic flux tube

The propagation of axisymmetric disturbances on a twisted magnetic flux tube in an inviscid, incompressible, unstratified atmosphere of infinite electrical conductivity is considered. Dispersion effects due to twist appear quickly only on highly twisted flux tubes for a superposition of the lowest radial eigenmodes and wavelengths comparable to the flux tube radius. These radial profiles become distorted and show focusing effects after propagating on the order of ten flux tube radii. This suggests twist effects on hydromagnetic wave propagation may be important where the flux tubes come up through the surface and expand into the tenuous atmosphere.

Bogdan, T. J.↗
NASA NTRS1985

A Comparison of Terrestrial Saltation Flux in the Laboratory and the Field

Aeolian transport of surficial material is an important part of the terrestrial geologic cycle. In many areas of geological interest, sand is not transported by the wind at the rate predicted by studies made in idealized conditions. Furthermore, calculated surface-abrasion rates based on laboratory saltation fluxes are often unrealistically high. This work is an attempt to quantify and discuss discrepancies between saltation rates under ideal conditions and in the field under natural conditions. The saltation-flux data persented by Sharp (1) will be used as the field data. Sharp measured saltation flux during four periods in the early 1950's in the Whitewater River drainage. Meteorological conditions at the experiment site were extrapolated from the airport records and from wind speeds measured simultaneously by Hunter. Wind speeds above threshold were sorted into 4-MPH bins and the frequency of observation over each experimental period was calculated. A saltation flux for each bin was calculated and summed to yield a predicted saltation rate for that period. When the predicted fluxes were compared with those measured by Sharp, large discrepancies were found.

Williams, S. H.↗