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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The sun-weather connection - Sudden stratospheric warmings correlated with sudden commencements and solar proton events

It has been found that a strong correlation exists between sudden stratospheric warmings and sudden commencements of geomagnetic activity. This correlation follows a 22-yr cycle. The sudden warmings of the lower stratosphere occur near the north magnetic pole over Siberia and the Pacific, although occasionally they do occur over North America. A mechanism explaining how the solar wind ultimately affects the surface weather through its selective interaction with the middle atmosphere is outlined.

Neubauer, L.↗
NASA NTRS1984

Stratwarm Effects in the Ionospheric D Region Wind Field

An analysis is made of the wind field structure in the strato-thermosphere over Eastern Siberia during the winter stratwarms of 1975-1977. It is found that coupling between dynamical processes in the stratosphere and lower thermosphere is effected through changes of the temperature regime of the atmosphere. The circulation regime both in the stratosphere and lower thermosphere depends on location of the source of perturbations that cause stratospheric warmings. The effect of warming-induced perturbations on the dynamics of above- and underlying layers and the meridional extent of the processes are determined by the altitude and region where anti-cyclones originate. In conditions of a warmer stratosphere, there is a considerable loss of wind stability in the ionospheric D-region. A time delay of 1 to 2 days of lower-thermosphere processes is found to occur with respect to stratospheric processes of temperature variation at 30 mb level.

Vergasova, G. V.↗
NASA NTRS1985

Diurnal modulation of the quiet time penetrating electron flux

Three sounding rocket measurements of energetic electron precipitation in the 65 to 80 km altitude range above Siple Station, Antarctica suggest a possible diurnal modulation of the precipitation. Flights made on January 10 and 11, 1981, to investigate this possibility showed that no electrons were present after local noon, while a significant flux of penetrating electrons was observed the following day near local dawn, even though the level of magnetic activity was higher during the postnoon flight. A prevous flight from Siple Station also observed a large flux of penetrating electrons near local dawn. Calculations of electron drift trajectories in a model magnetic field indicate that moderate values of the convection electric field could cause significant local time variations in the penetrating electron flux at the western edge of the South Atlantic anomaly. These calculations indicate that Siple Station is shadowed by eastern Siberia when it is at local noon, but not when it is at local dawn.

Sheldon, W. R.↗
NASA NTRS1989

Midlatitude seasonal behavior of tides near the mesopause level

Wind measurements near the mesopause level were provided in Badary (Eastern Siberia, USSR) by the D1 method using a low frequency (200 kHz) radio transmitter during 1976 to 1986. The seasonal variations of wind level are analyzed and compared with other midlatitude wind measurements and with some theoretical preditions. It is shown that tidal parameters depend not only on latitude but on the longitude as well. The annual variation of diurnal and semidurnal tide (zonal and meridional) have maxima in summer and minima in winter. There are significant differences between annual variations of phases for diurnal and semidiurnal tides. These differences are especially distinct for summer and autumn. There is no systematic seasonal variation of the phase of the semidiurnal tide (average value similar to 6 hours).

Kazimirovsky, E. S.↗
NASA NTRS1989

A transient auroral event on the dayside

A strong perturbation lasting about 10 min, beginning at 0930 UT on December 5, 1986, was recorded by high-latitude magnetometer stations in Greenland, Iqaluit, and the South Pole. Viking and Polar Bear satellite observations of the perturbation and observations of similar perturbations on the afternoon side in Svalbard, Heiss Island, and northern Siberia are also reported. It is suggested that the likely source of the perturbation is a magnetic disturbance in the solar wind observed by ISEE 1/2 and IMP 8. The perturbation is interpreted as an impulsive penetration of solar wind plasma on an interplanetary magnetic flux tube occurring through the magnetopause, ending in the low latitude boundary layer.

Heikkila, Walter J.↗
NASA NTRS1992

Ar-40 to Ar-39 ages of the large impact structures Kara and Manicouagan and their relevance to the Cretaceous-Tertiary and the Triassic-Jurassic boundary

Since the discovery of the Ir enrichment in Cretaceous-Tertiary boundary clays in 1980, the effects of a 10-km asteroid impacting on the Earth 65 Ma ago have been discussed as the possible reason for the mass extinction--including the extinction of the dinosaurs--at the end of the Cretaceous. But up to now no crater of this age that is large enough (ca. 200 km in diameter) has been found. One candidate is the Kara Crater in northern Siberia. Kolesnikov et al. determined a K-Ar isochron of 65.6 +/- 0.5 Ma, indistinguishable from the age of the K-T boundary and interpreted this as confirmation of earlier proposals that the Kara bolide would have been at least one of the K-T impactors. Koeberl et al. determined Ar-40 to Ar-39 ages ranging from 70 to 82 Ma and suggested an association to the Campanian-Maastrichtian boundary, another important extinction horizon 73 Ma ago. We dated four impact melts, KA2-306, KA2-305, SA1-302, and AN9-182. Results from the investigation are discussed.

Trieloff, M.↗
NASA NTRS1992

A test of present-day plate geometries for northeast Asia and Japan

Alternative geometries for the present-day configuration of plate boundaries in northeast Asia and Japan are tested using NUVEL-1 and 256 horizontal earthquake slip vectors from the Japan and northern Kuril trenches. Statistical analysis of the slip vectors is used to determine whether the North American, Eurasian, or Okhotsk plate overlies the trench. Along the northern Kuril trench, slip vectors are well-fit by the NUVEL-1 Pacific-North America Euler pole, but are poorly fit by the Pacific-Eurasia Euler pole. Results for the Japan trench are less conclusive, but suggest that much of Honshu and Hokkaido are also part of the North American plate. The simplest geometry consistent with the trench slip vectors is a geometry in which the North American plate extends south to 41 deg N, and possibly includes northern Honshu and southern Hokkaido. Although these results imply that the diffuse seismicity that connects the Lena River delta to Sakhalin Island and the eastern Sea of Japan records motion between Eurasia and North America, onshore geologic and seismic data define an additional belt of seismicity in Siberia that cannot be explained with this geometry. Assuming that these two seismic belts constitute evidence for an Okhotsk block, two published kinematic models for motion of the Okhotsk block are tested. The first model, which predicts motion of up to 15 mm/yr relative to North America, is rejected because Kuril and Japan trench slip vectors are fit more poorly than for the simpler geometry described above. The second model gives a good fit to the trench slip vectors, but only if Okhotsk-North America motion is slower than 5 mm/yr.

Demets, Charles↗
NASA NTRS1992

Meteorological overview of the Arctic Boundary Layer Expedition (ABLE 3A) flight series

A meteorological overview of the Arctic Boundary Layer Expedition (ABLE 3A) flight series is presented. Synoptic analyses of mid-tropospheric circulation patterns are combined with isentropic back trajectory calculations to describe the long-range (400-3000 km) atmospheric transport mechanisms and pathways of air masses to the Arctic and sub-Arctic regions of North America during July and August 1988. Siberia and the northern Pacific Ocean were found to be the two most likely source areas for 3-day transport to the study areas in Alaska. Transport to the Barrow region was frequently influenced by polar vortices and associated short-wave troughs over the Arctic Ocean, while the Bethel area was most often affected by lows migrating across the Bering Sea and the Gulf of Alaska, as well as ridges of high pressure which built into interior Alaska. July 1988 was warmer and dryer than normal over much of Alaska. As a result, the 1988 Alaska fire season was one of the most active of the past decade. Airborne lidar measurements verified the presence of biomass burning plumes on many flights, often trapped in thin subsidence layer temperature inversions. Several cases of stratosphere/troposphere exchange were noted, based upon potential vorticity analyses and aircraft lidar data, especially in the Barrow region and during transit flights to and from Alaska.

Shipham, Mark C.↗
NASA NTRS1992

Summertime tropospheric observations related to N(x)O(y) distributions and partitioning over Alaska - Arctic Boundary Layer Expedition 3A

Measurements of NO, NO2, PAN and NO(y) are presented for the summertime middle/lower troposphere over northern high latitudes. Chemical signatures from concurrent measurements of O3, CO, C2H2, C2H6, C3H8, C2Cl4, and H2O are used to characterize factors affecting the budget and distribution of N(x)O(y) in the Arctic and Sub-Arctic tropospheric air masses sampled over Alaska during the NASA Arctic Boundary Layer Expedition (ABLE 3A). The results implicate biomass burning in Siberia as the probable source of about one-third of the NO(y) abundance within the middle lower troposphere over Alaska and the downward transport of air from altitude in the vicinity of the tropopause as a major contributor to the abundance of NO(y) within the lower 6 km column over Alaska.

Sandholm, S. T.↗
NASA NTRS1993

The 1908 Tunguska explosion - Atmospheric disruption of a stony asteroid

The explosion over Tunguska, Central Siberia, in 1908 released 10 to 20 megatons (high explosive equivalent) of energy at an altitude of about 10 km. This event represents a typical fate for stony asteroids tens of meters in radius entering the Earth's atmosphere at common hypersonic velocities. Comets and carbonaceous asteroids of the appropriate energy disrupt too high, whereas typical iron objects reach and crater the terrestrial surface.

Chyba, Christofer F.↗
NASA NTRS1993

Gravity field over northern Eurasia and variations in the strength of the upper mantle

The correlation of long-wavelength gravity anomalies in northern Eurasia with seismic velocity anomalies in the upper mantle reverses in sign between western and eastern Eurasia. The difference between western and eastern Eurasia can be explained by the presence of a low-viscosity zone in the uppermost mantle beneath eastern Eurasia that is absent to the west. The location of the lateral change in viscosity corresponds with the geologic boundary between the older shields and platforms of the Baltics, Russia, and Siberia and the younger, geologically active mountain belts of eastern Asia. This relation provides evidence that differences in the strength of the upper mantle control the locus of intracontinental deformation.

Kogan, Mikhail G.↗
NASA NTRS1993

The Arctic Ocean ice balance - A Kalman smoother estimate

The methodology of Kalman filtering and smoothing is used to integrate a 7-year time series of buoy-derived ice motion fields and satellite passive microwave observations. The result is a record of the concentrations of open water, first-year ice, and multiyear ice that we believe is better than the estimates based on the microwave data alone. The Kalman procedure interprets the evolution of the ice cover in terms of advection, melt, growth, ridging, and aging of first-year into multiyear ice. Generally, the regions along the coasts of Alaska and Siberia and the area just north of Fram Strait are sources of first-year ice, with the rest of the Arctic Ocean acting as a sink for first-year ice via ridging and aging. All the Arctic Ocean except for the Beaufort and Chukchi seas is a source of multiyear ice, with the Chukchi being the only internal multiyear ice sink. Export through Fram Strait is a major ice sink, but we find only about two-thirds the export and greater interannual variation than found in previous studies. There is no discernible trend in the area of multiyear ice in the Arctic Ocean during the 7 years.

Thomas, D. R.↗
NASA NTRS1993

Implications of new gravity data for Baikal Rift zone structure

Newly available, 2D Bouguer gravity anomaly data from the Baikal Rift zone, Siberia, indicate that this discrete, intracontinental rift system is regionally compensated by an elastic plate about 50 km thick. However, spectral and spatial domain analyses and isostatic anomaly calculations show that simple elastic plate theory does not offer an adequate explanation for compensation in the rift zone, probably because of significant lateral variations in plate strength and the presence of subsurface loads. Our results and other geophysical observations support the interpretation that the Baikal Rift zone is colder than either the East African or Rio Grande rift.

Ruppel, C.↗
NASA NTRS1991

Clinical aspects of telemedicine

Communication among physicians is an essential in order to combine our experiences for the elucidation and application of new knowledge and for the accurate and uniform application of established medical practice. This communication requires an adequate understanding of the culture of the patient and the social context of disease and indeed the culture of the physician. Malnutrition in Bangladesh means caloric insufficiency, and a program to lower cholesterol would be impertinent, while a program to enhance the nutrition of patients in Texas by an international effort to import more grain would be ludicrous. In the same vein a public health effort to combat alcoholic cirrhosis in Mecca would be as silly as a program to increase fiber in the diet of the Bantu. Clinical communication must acknowledge the culture of the issue at hand and the differences in the experiential base of the physicians. Not only do geography and culture affect the potential differences in the experiential bases, but the world utilizes very different traditions of education and science in training physicians. We are influenced by the diseases we treat, and learn to look for the expected at least as much as we are attentive to the unexpected. A physician in Siberia would be much more likely to recognize frostbite than one from Buenos Aires, and the Argentine doctor would much more likely consider Chaga's Disease to explain abdominal pain than a colleague in Zurich. Beyond these obvious issues in communication among physicians we must deal with the many languages and idioms used in the world. An overview of using Telemedicine SpaceBridge after the earthquake in the Republic of Armenia in 1988 is presented.

Merrell, Ronald C.↗
NASA NTRS1993

Age of Popigai impact event using the Ar-40 - Ar-39 method

The Popigai impact structure of central Siberia is the largest known impact crater in the Commonwealth of Independent States with an original diameter of some 1OO km. The age of the crater is constrained by the existing stratigraphy to a period between 5-65 Ma. Attempts to date the impact event using conventional K-Ar on whole rock samples and fission track dating on glasses yield a spread of ages between 30 and 45 Ma. Argon step-heating analyses of several whole-rock samples performed with the Argon Laserprobe at the University of Toronto indicated an age of impact of about 36 Ma. However, a more recently reported Ar-40 - Ar-49 result on glass separated from a suevite sample gave a 65 Ma age and raised the possibility that Popigai was involved with the K/T boundary event. We have pursued further analyses at the University of Toronto on a broader spectrum of Popigai samples. These results confirm an age of about 36 Ma for the formation of this crater, and indicate that Popigai was not associated with the K/T boundary event.

Bottomley, R. J.↗
NASA NTRS1993

Global geologic applications of the Space Shuttle earth observations photography database

The advantages of the astronaut photography during Space Shuttle missions are briefly examined, and the scope and applications of the Space Shuttle earth observations photography database are discussed. The global and multidisciplinary nature of the data base is illustrated by several examples of geologic applications. These include the eruption of Mount Pinatubo (Philippine Islands), heat flow and ice cover on Lake Baikal in Siberia (Russia), and windblown dust in South America. It is noted that hand-held photography from the U.S. Space Shuttle provides unique remotely-sensed data for geologic applications because of the combination of varying perspectives, look angles, and illumination, and changing resolution resulting from different lenses and altitudes.

Lulla, Kamlesh↗
NASA NTRS1993

Calibrating rates of early Cambrian evolution

An explosive episode of biological diversification occurred near the beginning of the Cambrian period. Evolutionary rates in the Cambrian have been difficult to quantify accurately because of a lack of high-precision ages. Currently, uranium-lead zircon geochronology is the most powerful method for dating rocks of Cambrian age. Uranium-lead zircon data from lower Cambrian rocks located in northeast Siberia indicate that the Cambrian period began about 544 million years ago and that its oldest (Manykaian) stage lasted no less than 10 million years. Other data indicate that the Tommotian and Atdabanian stages together lasted only 5 to 10 million years. The resulting compression of Early Cambrian time accentuates the rapidity of both the faunal diversification and subsequent Cambrian turnover.

Bowring, Samuel A.↗
NASA NTRS1994

Neotectonics of Asia: Thin-shell finite-element models with faults

As India pushed into and beneath the south margin of Asia in Cenozoic time, it added a great volume of crust, which may have been (1) emplaced locally beneath Tibet, (2) distributed as regional crustal thickening of Asia, (3) converted to mantle eclogite by high-pressure metamorphism, or (4) extruded eastward to increase the area of Asia. The amount of eastward extrusion is especially controversial: plane-stress computer models of finite strain in a continuum lithosphere show minimal escape, while laboratory and theoretical plane-strain models of finite strain in a faulted lithosphere show escape as the dominant mode. We suggest computing the present (or neo)tectonics by use of the known fault network and available data on fault activity, geodesy, and stress to select the best model. We apply a new thin-shell method which can represent a faulted lithosphere of realistic rheology on a sphere, and provided predictions of present velocities, fault slip rates, and stresses for various trial rheologies and boundary conditions. To minimize artificial boundaries, the models include all of Asia east of 40 deg E and span 100 deg on the globe. The primary unknowns are the friction coefficient of faults within Asia and the amounts of shear traction applied to Asia in the Himalayan and oceanic subduction zones at its margins. Data on Quaternary fault activity prove to be most useful in rating the models. Best results are obtained with a very low fault friction of 0.085. This major heterogeneity shows that unfaulted continum models cannot be expected to give accurate simulations of the orogeny. But, even with such weak faults, only a fraction of the internal deformation is expressed as fault slip; this means that rigid microplate models cannot represent the kinematics either. A universal feature of the better models is that eastern China and southeast Asia flow rapidly eastward with respect to Siberia. The rate of escape is very sensitive to the level of shear traction in the Pacific subduction zones, which is below 6 MPa. Because this flow occurs across a wide range of latitudes, the net eastward escape is greater than the rate of crustal addition in the Himalaya. The crustal budget is balanced by extension and thinning, primarily within the Tibetan plateau and the Baikal rift. The low level of deviation stresses in the best models suggests that topographic stress plays a major role in the orogeny; thus, we have to expect that different topography in the past may have been linked with fundamentally different modes of continental collision.

Kong, Xianghong↗