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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

A compilation of studies from Atmospheric Variability Experiment (AVE)

Five methods for obtaining the sign of vertical motion at various levels in the atmosphere were investigated to determine which gave the best explanation for areas of rain and no-rain in the southeastern United States during the period February 19-22, 1964. The methods used were the terrain-induced vertical motion, the kinematic method including the terrain effect, the adiabatic method, the omega equation, and the vorticity equation combined with Dines' Compensation Principle. Stability and moisture availability were considered but not as extensively as vertical motion. Values of vertical motion obtained by the kinetic method, including orographic lifting produced the best agreement with the observed areas. When terms in the omega equation were added through use of constant multipliers, results comparable to the adiabatic method were obtained. Without this addition large uncertainties occurred. Maps showing areas where terms of the omega equation would indicate positive vertical motion did not correlate well with the observed rainfall patterns.

Scoggins, J. R.↗
NASA NTRS1973

Solar flare produced pulsations in meter and X-ray wavelengths

The mechanism responsible for the modulation of synchrotron radiation in the meter wave range by a solar flare is examined. The proposed explanation is based on the interaction of a flare generated shock front with a magnetic flux tube extending out into the corona over the flare. As the shock wave propagates through the flux tube, Alfven waves are developing and travelling up the tube toward each other, thereby accelerating electrons and protons by the Fermi mechanism and thus filling the top of the flux tube with energetic electrons. Radial oscillations develop as the shock front becomes parallel to the magnetic field direction and the intensity of the synchrotron radiation is modulated by these oscillations. An OSO-5 experiment detected a hard X-ray burst associated with the flare that produced modulated radio emission and X-ray modulations that are attributed to density fluctuations in the X-ray bursts.

Frost, K. J.↗
NASA NTRS1973

Water and processes of degradation in the Martian landscape

It is shown that erosion has been active on Mars so that many of the surface landforms are products of degradation. Unlike earth, erosion has not been a universal process, but one areally restricted and intermittently active so that a landscape is the product of one or two cycles of erosion and large areas of essentially undisturbed primitive terrain; running water has been the principal agent of degradation. Many features on Mars are most easily explained by assuming running surface water at some time in the past; for a few features, running water is the only possible explanation.

Milton, D. J.↗
NASA NTRS1973

Ground Operations Aerospace Language (GOAL) textbook

The textbook provides a semantical explanation accompanying a complete set of GOAL syntax diagrams, system concepts, language component interaction, and general language concepts necessary for efficient language implementation/execution.

Dickison, L. R.↗
NASA NTRS1972

Variation of cloud emissivity in the infrared.

The spectral radiative properties of solid and liquid H2O particles in the thermal infrared are examined. The study of these properties is aimed at an explanation of the spectral features associated with certain clouds pointed out by Hanel et al. (1972) in an analysis of the results of the Nimbus 4 infrared spectroscopy experiment.

Curran, R. J.↗
NASA NTRS1972

Binary stars as X-ray sources.

The idea that many if not most of the powerful galactic X-ray sources are generated in binary star systems containing at least one exotic object with gas is examined. Past studies lending support to this hypothesis are reviewed, and major features of galactic X-ray sources that require explanations are delineated. Attention is given to conclusions gained from optical studies of close binaries and to promising areas of further investigation stemming from the concept of binary stars as X-ray sources.

Burbidge, G.↗
NASA NTRS1972

A near-infrared view of the Uranus system.

An image intensifying tube placed at the f/10 Cassegrain focus of an 88-in. reflector telescope was used together with a narrow filter centered at the 8870-A methane band to obtain near-infrared photographs of Uranus and its satellites. Good images of Uranus were obtained with a 1-min exposure, while the faintest satellite Miranda was well recorded in about one hour. The short-exposure photograph of Uranus shows that the limb is brighter than the center of the disk and brightest at the south pole. The explanation for the brightening of the limb and pole seems to be haze in the planet's upper atmosphere.

Sinton, W. M.↗
NASA NTRS1972

Collisionless plasma flow over a conducting sphere.

Laboratory simulation study of spacecraft-space plasma interaction using a plasma wind tunnel. Some preliminary results on a collisionless plasma flow pattern over a conducting sphere are presented. A physical explanation is given for the observed plasma flow behavior.

Stone, N. H.↗
NASA NTRS1972

The geomorphic evolution of the lunar surface.

The solution of the function relating craters of the continuous degradation sequence with degree of erosion was defined as the geomorphic index of the area. Studies of the geomorphic index of stratigraphic surfaces show that areas covered by considerable ballistic sediments have a geomorphic index which is not a monotonic function of time. On the other hand, areas covered almost exclusively by mare flooding show an index which is a monotonic function of the age of the flooding. As each mare surface shows a considerable range in indices, it is concluded that maria are covered by surfaces formed through a considerable length of time. By using Apollo 11 and 12 radiometric ages it is suggested that the time of mare flooding lasted on the order of one billion years. The geomorphic index of highland surfaces shows a remarkable degree of order - i.e., the farther an area is inland from the mare shores, the higher will be the index. No explanation is given for this phenomenon, but it is suggested that lunar erosion is not just a localized phenomenon centered on the locus of an impact, but has lateral trends of regional dimensions.

Ronca, L. B.↗
NASA NTRS1972

Erosion, transportation and the nature of the maria.

Seismic evidence makes clear that there is no continuous sheet of bedrock at a shallow depth in the vicinity of the Apollo 12 site. A deep deposit of powder would match the seismic properties observed. Mascons require for their explanation a surface transportation process that tends to fill in the large impact basins after their formation. Surface transportation of lunar dust has been demonstrated in the laboratory to occur most readily as a result of electrostatic forces produced by electron bombardment in the energy range of a few hundred volts. Such bombardment happens on the moon predominantly when it is in the magnetic tail of the earth, and this may be the reason why mare ground is so remarkably dominant on the hemisphere facing the earth.

Gold, T.↗
NASA NTRS1972

Transient mass transfer at the rotating disk electrode.

Transient mass transfer at the rotating disk has been investigated theoretically and experimentally for cathodic reduction of ferricyanide in the redox system ferricyanide-ferrocyanide with potassium hydroxide supporting electrolyte. It has been shown that overpotential-time predictions for the rotating disk are fitted very well for decay (current interruption) but poorly for build-up following switching on of constant current. As an explanation for this behavior, attention is directed to the inadequacy of the assumption that a radially independent concentration profile exists at the disk surface just at the start of galvanostatic current passage.

Nanis, L.↗
NASA NTRS1972

Plasma convection in the vicinity of the geosynchronous orbit.

An analytic function respresenting the quiet time magnetospheric electric field has been constructed with which it is possible to compute complete particle trajectories in a fraction of a second. The function was determined by a trial-and-error procedure such that it provides reasonable explanations for the characteristics of the plasma observed by the geosynchronous satellite ATS 5. It is believed that the model field is usefully accurate within the region of 5 to 7 earth radii on the dawn side of the magnetosphere and 5 to 10 earth radii on the dusk side. At a fixed distance of 6.7 earth radii the model field peaks at a value of 1.2 mV/m near local midnight and is at a minimum of 0.04 mV/m near 1900 LT.

Mcilwain, C. E.↗
NASA NTRS1972

Nighttime sporadic-E.

At night, internal atmospheric gravity waves are able to induce drift instabilities in the ionospheric plasma. Nighttime constant height type sporadic-E(Esc) may then be explained as an effect due to the combined effect of ionization movement due to the wind shear mechanism and due to the cross-field gradient drifts. This combined concept provides a qualitative explanation of the rocket observed nighttime electron density profiles, of the speeds of the Esc irregularities and of the variations of Esc with latitude and electric field strength.-

Beer, T.↗
NASA NTRS1972

Modulation of low-energy galactic cosmic rays over solar maximum /cycle 20/.

Low-energy (about 60 MeV/nucleon) galactic cosmic rays observed during the recent period of solar maximum are reviewed. For this particular cycle, a significant time lag between intensity changes in the low-energy and high-energy components has been observed. Several possible explanations of this 'hysteresis effect' are discussed. The cosmic-ray intensity gradients provided by Pioneer 10 are soon to be available and are expected to provide a more definite clue to this process of cosmic-ray modulation.

Van Hollebeke, M. A. I.↗
NASA NTRS1972

Further evidence for a black hole in Beta Lyrae.

Comments regarding an interpretation of the OAO-2 observations of Beta Lyrae are presented. This interpretation had been reported by Wilson (1971). Six color UV curves represent the first continual coverage of a single cycle of Beta Lyr. Explanations for the deepening secondary minimum in the far UV are discussed. It is pointed out that the secondary component is apparently a massive object. The 'black hole' model represents one approach to interpret the observations of Beta Lyr.

Kondo, Y.↗
NASA NTRS1972

Interplanet variations in scale of crater morphology - Earth, Mars, Moon.

Craters on the Earth, Mars, and the Moon show a spectrum of morphologies with diameter increasing from simple, bowl-shaped craters through craters with increasingly complex central peaks, to craters with 'peak rings' and basins with multiple concentric scarps. In each category there is a range of diameters, centered around a characteristic diameter, D sub c. It is found that D sub c decreases as the size of the planet increases. Several possible explanations are considered. It is suggested that the effect results from a certain gravity scaling law. It is believed that all geological structures in which gravity is the dominant parameter affecting the morphology should follow this law.

Hartmann, W. K.↗
NASA NTRS1972

Anisotropy of the neutron fluence from a plasma focus.

The fluence of neutrons from a plasma focus was measured by gamma spectrometry of an activated silver target. This method results in a significant increase in accuracy over the beta-counting method. Multiple detectors were used in order to measure the anisotropy of the fluence of neutrons. The fluence was found to be concentrated in a cone with a half-angle of 30 deg about the axis, and to drop off rapidly outside of this cone; the anisotropy was found to depend upon the total yield of neutrons. This dependence was strongest on the axis. Neither the axial concentration of the fluence of neutrons nor its dependence on the total yield of neutrons is explained by any of the currently proposed models. Some other explanations, including the possibility of an axially distributed source, are considered.

Lee, J. H.↗
NASA NTRS1972

Astronaut observations from lunar orbit and their geologic significance.

To supplement orbital photography and other remotely sensed data, visual observations were made of 15 lunar surface targets during Apollo mission 15. Among the significant results are (1) characterization of the floor material of Tsiolkovsky as no darker than the average (Eratosthenian) mare material, and interpretration of the lineated unit on the crater rim as a rock avalanche; (2) identification of layers on the wall of the crater Picard, which is probably volcanic in origin, (3) explanation of the ray-excluded zone of the crater Proclus as the result of structurally controlled ray shadowing; (4) observation of cinder cones in the Littrow area with dark haloes that probably are composed of pyroclastic deposits; and (5) recognition that the termini of numerous sinuous rilles in Oceanus Procellarum are flooded with younger mare materials that may have covered older terminal deposits.

El-Baz, F.↗