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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Transient convection over the Amazon-Bolivia region and the dynamics of drought over Northeast Brazil

A two layer, nonlinear, equatorial beta-plane model, in p-coordinates is used to study the atmospheric response to a large scale prescribed heat source varying in time. The heat source is meant to represent a convective burst with total duration of approximately 48 hours over the Amazon/Bolivia region. The boundary conditions used are meridional velocity zero at 60 deg S, omega w = 0 at the top and zero geometric velocity at the lower boundary. Sensitivity study was done which includes initial state at rest, compared with realistic initial flow. The scale of the heat source is 1500 km in latitude and longitude and it is centered at 10 deg S. Special attention is paid to the distribution and intensity of the induced vertical motion. The model is integrated for two days and the preliminary results show agreement with the observed 200 mb flow. Of interest is the establishment of a trough and descending motion to the northeast of the heat source. A conjucture is thus made that the Amazon heat source and its fluctuations bear some relationship with the drought problem over Northeast Brazil.

Buchmann, J.↗
NASA NTRS1985

Rossby wavetrains in the stratosphere forced by localised disturbances in the troposphere

Studies have linked elements of the stratospheric circulation with particular localized features in the tropospheric circulation. This suggests a study of the response of the stratosphere to forcing by localized disturbances in the troposphere. A multilevel, primitive equation model is used of the stratosphere and mesosphere the height of whose lower boundary at 300 mb can be prescribed. Localized height disturbances which grow to steady amplitude are applied at this lower boundary, and the response of the initially axially symmetric stratosphere is studied. The perturbation, centered at 45 deg N, has a Gaussian distribution with a half width of 15 deg., corresponding roughly to the size of persistent troughs and blocking ridges in the troposphere. The forcing is nearly at fully amplitude 10 days after being switched on, and thereafter remains steady. Two types of experiments are conducted: in one the forcing is of small amplitude (100 gpm) and in the other it is of large amplitude (600 gpm). These pairs of experiments are compared to determine how nonlinear processes affect the perturbation fields. This is done locally by defining the perturbation response to the forcing as an anomaly, i.e., as a departure from the response in a controlled experiment in which no asymmetric forcing was applied at the lower boundary of the model. Experiments have been conducted for a number of atmospheric states obtained as zonal means of observations made by a stratospheric sounding unit (SSU). In this summary, results for the zonal mean flow on January 19, 1982 are outlined.

Marks, C. J.↗
NASA NTRS1985

Extensional tectonics on continents and the transport of heat and matter

Intracontinental zones of extensional tectonic style are commonly of finite width and length. Associated sedimentary troughs are fault-controlled. The evolution of those structures is accompanied by volcanic activity of variable intensity. The characteristic surface structures are usually underlaid by a lower crust of the transitional type while deeper subcustal areas show delayed travel times of seismic waves especially at young tectonic provinces. A correspondence between deep-seated processes and zones of continental extension appears obvious. A sequential order of mechanisms and their importance are discussed in the light of modern data compilations and quantitative kinematic and dynamic approaches. The Cenozoic exensional tectonics related with the Rhine River are discussed.

Neugebauer, H. J.↗
NASA NTRS1985

Comparative magnetospheric/ionospheric studies using Dynamics Explorer spacecraft and ground-based radars

Coincident observations between the Dynamics Explorer 1 and 2 spacecraft with Chatanika and Arecibo ground-based radar are briefly reviewed. Ionospheric-magnetospheric coupling processes in the plasmasphere, main trough, auroral zone, and polar cap are inferred from the density, temperature, composition, and angular distributions of the low-energy plasma observed from the E-region ionosphere out into the magnetosphere to an altitude of 2.5 earth radii (Re). From the polar cap to the inner plasmasphere, parallel and perpendicular electric fields, polar wind flow, and equilibrium diffusion appear to be involved in the ionospheric-magnetospheric coupling of the low energy plasma.

Green, J. L.↗
NASA NTRS1984

A review of major east coast snowstorms

The surface and upper-level characteristics in selected wind, pressure, and temperature fields of some significant east coast cyclones are studied. The surface, 200, 300, 500, 700, and 850 mb charts of 18 case studies of storms are analyzed. The surface patterns are described in terms of the type of cyclone, the variation in rate of motion, the effect of coastal frontogenesis on the storms, sea level pressures, and the deepening rate of pressure. The influence of upper-level troughs, ridges, jet streaks, location of wind amplification, and time on cyclogenesis is examined.

Kocin, P. J.↗
NASA NTRS1986

An apparent gravitational lens with an image separation of 2.6 arc min

Observations are reported which confirm Paczynski's 1986 speculation that the previously known (Arp and Hazard, 1980) pair of 19th magnitude quasars 1146+111B,C are actually two images of a single object produced by a gravitational lens. The image split is 157 arcsec, more than 20 times greater than any previously reported, thus indicating an exceptionally massive lensing object. The data supporting the lens hypothesis are remarkably similar, high signal-to-noise, moderate resolution spectra of the two components. Both spectra show strong Mg II 2798-angstrom emission at z = 1.012 plus or minus 0.001 with indistinguishable redshifts (delta v = 126 plus or minus 309 km/s), widths (FWHM = 64 plus or minus 4 angstroms) and detailed profile shapes. Both spectra also show broad troughs at 6180 angstroms and several weaker continuum features. Neither object exhibits the O II 3727-A forbidden line which is frequently strong in Mg II emission objects. If the foreground galaxy clustering apparent in a deep R band charge-coupled device image proves insufficient to explain the large image splitting, other possibilities such as massive dark objects (e.g. a black hole of about 10 to the 15th solar masses) or a cosmic string may be indicated.

Turner, E. L.↗
NASA NTRS1986

Observations of ionospheric magnetospheric coupling - DE and Chatanika coincidences

Observations from several experiments on board the Dynamics Explorer 1 and 2 (DE 1 and 2) spacecraft and ground-based radar measurements from the Chatanika radar are combined in order to examine the details of ionospheric/magnetospheric coupling in the local evening sector. DE 1 and DE 2 were in coplanar polar orbits that provided measurements almost simultaneously in time and magnetically coincident with the Chatanika radar from L = 3 to L = 17. The coupling processes are inferred from the density, temperature, composition, and angular distributions of the low-energy plasma observed from the E region of the ionosphere to magnetospheric altitudes of 2.5 earth radii. Plasma characteristics of the plasmasphere, main trough, auroral zone, and polar cap can be studied in this data set. The observations imply that as L increases, the dominant coupling mechanism between the ionosphere and magnetosphere in the measured energy range changes from equilibrium diffusion to perpendicular acceleration and finally to parallel acceleration.

Green, J. L.↗
NASA NTRS1986

Tectonic escape in the evolution of the continental crust

The continental crust originated by processes similar to those operating today and continents consist of material most of which originated long ago in arc-systems that have later been modified, especially at Andean margins and in continental collisions where crustal thickening is common. Collision-related strike-slip motion is a general process in continental evolution. Because buoyant continental (or arc) material generally moves during collision toward a nearby oceanic margin where less buoyant lithosphere crops out, the process of major strike-slip dominated motion toward a 'free-face' is called 'tectonic escape'. Tectonic escape is and has been an element in continental evolution throughout recorded earth-history. It promotes: (1) rifting and the formation of rift-basins with thinning of thickened crust; (2) pervasive strike-slip faulting late in orogenic history which breaks up mountain belts across strike and may juxtapose unrelated sectors in cross-section; (3) localized compressional mountains and related foreland-trough basins.

Burke, K.↗
NASA NTRS1985

Comparative magnetospheric/ionospheric studies using Dynamics Explorer spacecraft and ground-based radars

Coincident magnetosphere-ionosphere observations between the Dynamics Explorer 1 and 2 spacecraft with ground-based radar are reviewed. Ionospheric-magnetospheric coupling processes in the plasmasphere, main trough, auroral zone, and polar cap are inferred from the density, temperature, composition, and angular distributions of the low-energy plasma observed from the E-region ionosphere out into the magnetosphere to an altitude of 2.5 Re. From the polar cap to the inner plasmasphere, parallel and perpendicular electric fields, polar wind flow, and equilibrium diffusion appear to be involved in the ionospheric-magnetospheric coupling of the low energy plasma.

Green, J. L.↗
NASA NTRS1986

The structure of the unstable marine boundary layer viewed by lidar and aircraft observations

The marine atmospheric boundary layer (MABL) during a cold-air outbreak off the Atlantic coast between New York and Virginia on January 20, 1983 is characterized on the basis of airborne lidar observations, vertical soundings (potential temperature, vapor mixing ratio, relative humidity, and wind), and horizontal (770-m) temperature records. The data are presented in tables and graphs and analyzed in detail. The organization of the MABL is defined by 1-2-km-scale roll vortices with up and downdrafts of 2-4 m/s at 210 m; north-south orientation of the roll axes (parallel to the low-level winds); rising arms coinciding with updrafts rich in moisture, aerosols, and heat; and 150-200-m (peak-to-trough) undulations of the inversion. Consideration is given to problems inherent in the interpretation of lidar data for MABL studies.

Atlas, D.↗
NASA NTRS1986

Low-threshold solar-pumped laser using C2F5I

Solar-pumped lasing was achieved with pentafluoroethyl iodide, C2F5I, a new alkyl-iodide. Output power and energy of 350 mW and 45 mJ were achieved. This lasant was found to have the lowest lasing threshold of any solar-pumped gas laser to date at approximately 100 solar constants. Such low threshold enables the use in space of simple, trough solar collectors.

De Young, R. J.↗
NASA NTRS1986

Ganymede and Callisto

The differences existing between Ganymede and Callisto are studied as well as their volcanic, tectonic, impact and surface processes. An attempt is made to explain the relatively vigorous history of geologic activity on Ganymede and the apparent lack of internal activity on Callisto. Observations reveal that the optical surfaces and regoliths of both bodies are ice rich, and thus unlikely to be remnants of a crust created by homogeneous accretion. Ganymede's relatively clean mantle was the source region for the water, slush, or ice that resurfaced more than half the satellite; this resurfacing material is structurally confined in broad rifts or troughs and is often captured to form grooved terrain. An explanation for resurfacing and tectonism on Ganymede and its near total absence on Callisto is that Ganymede is at least partially differentiated while Callisto is undifferentiated.

Mckinnon, William B.↗
NASA NTRS1986

Ozone, jet streaks, and severe weather

Data obtained with the total ozone mapping spectrometer (TOMS) onboard the Nimbus-7 satellite are presented. An attempt is made to relate and synthesize TOMS data with conventional radiosonde analyses and with midtropospheric moisture data available from the VISSR onboard the GOES. Case studies are described which relate the potential vorticity structure of the upper troposphere to the total ozone distribution as measured by TOMS. Cyclogenesis, frontogenesis, and the formation of severe weather outbreaks are then related to jet streaks and their characteristic ozone signature. It is shown that the primary maxima of ozone and potential vorticity are associated with cold advection and subsidence in the main upper-air trough as suggested earlier. The secondary maxima of the three quantities diagnosed in the present work appear in the left front quadrant of a jet streak, revealing the importance of transverse, secondary motions induced by a jet streak above the level of maximum winds in further modifying the potential vorticity and ozone structures.

Sechrist, F. S.↗
NASA NTRS1986

Venus - Dead or alive?

In situ nightside electric field observations from the Pioneer Venus Orbiter have been interpreted as evidence of extensive lightning in the lower atmosphere of Venus. The scenario, including proposed evidence of clustering of lightning over surface highland regions, has encouraged the acceptance of currently active volcanic output as part of several investigations of the dynamics and chemistry of the atmosphere and the geology of the planet. However, the correlation between the 100-hertz electric field events attributed to lightning and nightside ionization troughs resulting from the interaction of the solar wind with the ionosphere indicates that the noise results from locally generated plasma instabilities and not from any behavior of the lower atmosphere. Furthemore, analysis of the spatial distribution of the noise shows that it is not clustered over highland topography, but rather occurs at random throughout the latitude and longitude regions sampled by the orbiter during the first 5 years of operation, from 1978 to 1984. Thus the electric field observations do not identify lightning and do not provide a basis for inferring the presence of currently active volcanic output. In the absence of known evidence to the contrary, it appears that Venus is no longer active.

Taylor, Harry A., Jr.↗
NASA NTRS1987

Recent mafic volcanism on Mars

The evidence for volcanism on Mars is commonly accepted, but none has been documented in the Valles Marineris equatorial rift system. A recent survey of the troughs in this valley revealed dark patches that are interpreted to be volcanic vents. The configuration and association of these patches with tectonic structures suggest that they are of internal origin; their albedo and color ratios indicate a mafic composition; and their stratigraphic position, crispness of morphologic detail, and low albedo imply that they are young, perhaps even recent.

Lucchitta, B. K.↗
NASA NTRS1986

Statistical study of enhanced ion fluxes in the outer plasmasphere

DE-1 measurements of ion outflows at E = 5 eV to 32 keV in the Northern Hemisphere outer plasmasphere are compiled in graphs and investigated statistically. The data comprise 40 dayside (6:00-12:00 magnetic local time) and 50 nightside (18:00-23:00) passages at magnetic activities Kp = 0-7 and include six magnetic storms and recoveries as well as quiet periods. Features noted include enhanced number fluxes during periods of increased magnetic activity, upward dayside and downward nightside flows, peak net H(+) fluxes greater than 10 to the 8th/sq cm sec, and greater field-aligned flows (but at lower ion temperatures) in the outer plasmasphere than in the plasma trough.

Menietti, J. D.↗
NASA NTRS1987

The ionosphere as a fully adequate source of plasma for the earth's magnetosphere

The ionospheric contribution of the polar wind and cleft ion fountain at energies less than 10 eV has been added to previously measured sources; this total ion outflow has then been used to calculate the resulting ion density in the different internal regions of the earth's magnetosphere: plasmasphere, plasma trough, plasma sheet, and magnetotail lobes. Using estimated volumes for these regions and an ion residence time characteristic of each region, it is found that the observed magnetospheric densities can be attained in all cases with no contribution from the solar wind plasma. In the case of the plasma sheet the ionospherically supplied density is more than enough to match the observations and even suggests an invisible component of low-energy plasma (less than 10 eV) which has never been observed. A detailed comparison between the calculated ionospheric source effects in the plasma sheet and those recently measured by ISEE shows excellent agreement and suggests a direct polar low-energy ion source for the plasma sheet which has remained unmeasured because of spacecraft potential effects. Although the solar wind is clearly the earth's magnetospheric energy source and energetic solar wind ions are observed in the magnetosphere, these calculations suggest the possibility that the ionospheric source alone is sufficient to supply the entire magnetospheric plasma content under all geomagnetic conditions.

Chappell, C. R.↗