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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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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

The Geology of Mt. Hope, a Silicic Volcanic Center in West Central Arizona

The purpose was to establish a detailed history of the sequence of geologic events which occurred at Mt. Hope and an area 6.8 miles in diameter surrounding it. The final result will be comprised of information collected during field mapping, with data from petrographic studies and wet chemical analyses. From this it should be possible to suggest relationships to other volcanic regions, particularly bimodal suites in the transition zone, and gain a clearer picture of the petrologic nature of this area. Field work conducted this past summer confirmed the bimodal nature of volcanism at Mt. Hope. The symmetrical, radial cone is comprised of several rhyolites with numerous intrusions of intermediate-composition dikes and two breccia pipes near the summit.

Simmons, A. M.↗
NASA NTRS1985

Deep space observations of the east-west asymmetry of solar energetic storm particle events - Voyagers 1 and 2

It has been well established that solar flare shock waves, propagating through the interplanetary medium, accelerate ambient energetic particles, giving rise to the formation of energetic storm particle (ESP) intensity enhancements. However, the acceleration mechanism which is responsible for the generation of ESP events is still under investigation. In the present investigation, energetic proton observations during solar flare ESP events made with the aid of the Voyagers 1 and 2 deep space probes are employed as a basis to examine further the acceleration processes responsible for the generation of ESP events under different 'interplanetary magnetic field-shock front' configurations. It is found that large ESP proton intensity enhancements are superimposed on the ambient solar energetic particle population for solar flare sites to the east of the sun-spacecraft medidian.

Sarris, E. T.↗
NASA NTRS1985

Multispacecraft observations of the east-west asymmetry of solar energetic storm particle events

Energetic proton observations have been obtained by instruments aboard the IMP-7 and -8 spacecraft and Voyager-1 and -2 deep space probes, in order to study the generation of solar flare Energetic Storm Particle Events (ESP) events at widely separated locations on the same shock front which are presumably characterized, on average, by different IMF shock front configurations for solar flare sites. Energetic proton observations indicate that substantial differences in the ESP proton intensity enhancements are detected at these energies for locations on the shock front with wide heliolongitude separations. The present results indicate that acceleration of ESP protons to more than 500 keV takes place at the quasi-perpendicular shock front domain, consistent with the 'shock drift' acceleration mechanism.

Sarris, E. T.↗
NASA NTRS1986

Lithology, age and structure of early proterozoic greenstone belts, West African shield

Lithologic and chemical data have been compiled for belts in the Proterozoic terrane. Available stratigraphic information from geologic maps of these areas indicate that a typical sequence is comprised of predominately mafic lava flows (basalt-andesite) at the base, which are overlain by felsic volcanic rocks including pyroclastic rocks and lavas. Lithostratigraphic data indicate the volcanic succession is 6-8 km thick. This is followed by 3-4 km of basaltic lava flows which are locally pillowed, the top of the unit is marked by a distinctive manganese formation (MF) consisting of Mn-Fe rich cherts up to 200 m thick. The youngest volcanic unit consists of mafic tuffs and breccia with a distinctive fragmental texture. Of about 100 chemical analyses reported calc-alkaline rocks constitute 55% and tholeiites 45%. Quartz-normative basalt constitutes 99% of the rock type in the tholeiitic suite. In the calc-alkaline suite, 9% of the analyses is basalt, 45% andesite and the rest is dacite and rhyodacite. The available data lead to the conclusion that the minimum age for the volcanic activity must be between 2200 and 2100 million years. It is significant that Archean ages have not been reported from any of the volcanic belts (1-10).

Attoh, K.↗
NASA NTRS1986

Regional variation in the Amitsoq gneisses related to crustal levels during late Archean granulite facies metamorphism: Southern west Greenland

The dominant lithology at Kangimut sangmissoq is described as nebulitic tonalitic gneiss containing highly distended plagioclase phyric amphibolites. The gneiss amphibolite complex was intruded by Nuk gneiss between 3.05 and 2.90 Ga and later (2.6 to 2.7 Ga) by post granulite facies granitoid sheets. The amphibolites are though to be Ameralik dikes and the older gray gneiss are then Amitsoq by definition. The problem arises when the isotopic data are considered, none of which indicate rocks older that about 3.0 Ga.

Nutman, A. P.↗
NASA NTRS1986

Aircraft and satellite passive microwave observations of the Bering Sea ice cover during MIZEX West

Passive microwave measurements of the Bering Sea were made with the NASA CV-990 airborne laboratory during February. Microwave data were obtained with imaging and dual-polarized, fixed-beam radiometers in a range of frequencies from 10 to 183 GHz. The high resolution imagery at 92 GHz provides a particularly good description of the marginal ice zone delineating regions of open water, ice compactness, and ice-edge structure. Analysis of the fixed-beam data shows that spectral differences increase with a decrease in ice thickness. Polarization at 18 and 37 GHz distinguishes among new, young, and first-year ice types.

Cavalieri, D. J.↗
NASA NTRS1986

Fluidization and hydrothermal alteration of the suevite deposit at the Ries Crater, West Germany, and implications for Mars

The emplacement, cooling, and alteration of the suevite at the Ries Crater are discussed. The clay mineralogy of the suevite is examined in terms of the cooling of the suevite and the importance of hydrothermal alteration. It is observed that the suevite contains large number of chimneylike degassing pipes, and that the suevite outside of the crater rim contains about 15 wt pct clay. The vertical channels or degassing pipes related to the fall-out of suevite are described. The relationship between the formation of the impact deposits on earth and Mars and the origin of Martian soil, and the emplacement and alteration of impact ejecta is studied.

Newsom, Horton E.↗
NASA NTRS1987

Cataclysmic variables. Recent multi-frequency observations and theoretical developments; Proceedings of the 93rd IAU Colloquium, Bamberg, West Germany, June 16-19, 1986

Papers are presented on the formation and evolution of low-mass close binaries with compact components, the periods of cataclysmic variables, multiwavelength observations of dwarf novae during outbursts, and radio emission from cataclysmic variables. Also considered are long-term optical photometry of the dwarf nova VW Hyi, periodic modulations in the optical light curves of EX Hydrae, and Echelle-Mepsicron time-resolved spectroscopy of the dwarf nova SS Cygni. Other topics include UV and X-ray observations of cataclysmic variables, new EXOSAT observations of TV Columbae, accretion disk evolution, and the boundary layer in cataclysmic variables.

Drechsel, H.↗
NASA NTRS1988

Reappraisal of the geology of Kangimut Sammisoq, Ameralik Fjord, Southern West Greenland: Crustal structure and interpretation of isotopic data

In Godthabsfjord, in the North Atlantic Archean Craton, early Archean Amitsoq gneisses are found in association with the mid to late Archean Nuk gneisses. The Amitsoq gneisses contain the Ameralik dykes, now subconcordant strips of amphibolite. The Nuk and Amitsoq gneisses have amphibolite facies polymetamorphic assemblages. To the southeast of Godthabsfjord, there is an extensive region affected by granulite facies metamorphism at 2800 Ma. Early models of crustal evolution for Godthabsfjord and the region to the SE are discussed. Recent detailed mapping combined with U-Pb zircon dating is examined.

Nutman, Allen P.↗
NASA NTRS1987

Thermospheric neutral wind signatures dependent on the east-west component of the interplanetary magnetic field for Northern and Southern Hemispheres as measured from Dynamics Explorer-2

DE-2 neutral-wind measurements obtained between November and January 1981-1982 and 1982-1983 were analyzed to investigate the effect of the sign of the IMF By component on neutral thermosphere dynamics at F-region altitudes. Maps of the mean neutral circulation for the northern (winter) and southern (summer) polar regions were derived for By positive and negative using polar geomagnetic coordinates. The mean neutral winds demonstrate clear By-dependent neutral wind signatures in both hemispheres.

Thayer, J. P.↗
NASA NTRS1988

Nd and Sr isotope systematics of clastic metasediments from Isua, West Greenland - Identification of pre-3.8 Ga differentiated crustal components

A detailed Sm-Nd and Rb-Sr isotopic study of the Isua clastic metasediments has been performed in the context of recently established stratigraphy for the Isua section. Samples from the sequence B are investigated for the first time. A clear correlation between lithology and isotopic characteristics is pointed out. The results indicate the existence of at least three distinct components for each of the distinct sequences A and B. It is suggested that some of these components may be derived from continental crustal sources that predate the time of depositon of these sediments by as much as about 0.4 b.y. A large pre-3.8 Ga continental crust is also inferred by the data.

Jacobsen, Stein B.↗
NASA NTRS1989

Viewing zenith angle dependence of cloudiness determined from coincident GOES East and GOES West data

The effect of the viewing zenith angle (VZA) on the cloudiness values observed by a satellite was investigated using a combination of two cloud-amount data sets derived from nearly simultaneous collocated GOES-E and GOES-W radiance measurements over the Pacific Ocean during May 1979 and July 1983. A hybrid bispectral threshold method was used to analyze data for single-layer and total cloudiness. It was found that the cloud fraction values increased with increasing VZA for almost all cases. Low clouds exhibited the greatest increases with a VZA increase for cloud amounts in the 0.1 range, whereas high clouds showed greatest increases for cloud amounts around 0.5. Midlevel clouds showed only a slight dependence on VZA. Total cloudiness increased the most, reflecting its predominantly low-cloud composition.

Minnis, Patrick↗
NASA NTRS1989

Atmospheric density remote sensing of mesosphere and thermosphere to be used for spacecraft design by adopting VHF radar and HF Doppler sounder at low latitude west Pacific site during winter time

Simultaneous observations of VHF radar and HF Doppler array systems located at Chung Li (Taiwan) are used to observe three-dimensional wind speeds and gravity waves. The density perturbations are determined at different altitudes of the mesosphere and thermosphere during weak convective motions of the cold front in the winter. The present observations are believed to be valuable for space projects dealing with the low-latitude atmosphere.

Hung, R. J.↗
NASA NTRS1989

Explosive east coast cyclogenesis over the west-central North Atlantic Ocean - A composite study derived from ECMWF operational analyses

This paper describes the observational aspects of explosive east-coast cyclogenesis using composites constructed from the daily global analyses generated and archived by ECMWF. An explosively deepening storm or bomb is defined as an extratropical cyclone whose mean sea-level pressure falls at least 1 mb/h for 24 h. The ECMWF data sets are used to examine the three-dimensional kinematic and thermodynamic structure of bombs over the entire depth of the troposphere. The evolution and structure of the composite bomb is diagnosed using a moving coordinate system consisting of a box with dimensions of 35 x 35 deg of latitude-longitude. The results reveal that explosive cyclogenesis is a baroclinic phenomenon in which the rapid development in the presence of strong upper tropospheric forcing is most likely enhanced by a highly destabilized lower troposphere.

Manobianco, John↗
NASA NTRS1990

Gradational epochs on Mars - Evidence from west-northwest of Isidis Basin and Electris

An account is given of the characteristics of Martian regions which may be adduced as evidence for enhanced gradation. The crater statistics for these regional surfaces are sufficiently different from those of proximate units with little evidence of modification to suggest, through comprehensive correlation, that a common pattern of modification to crater statistics may be a reflection of common epochs of enhanced gradation. If that be the case, then these areas' gradation occurred during a series of epochs of local-to-global extent whose duration and intensity decreased through time, following the last major impacts.

Grant, John A.↗