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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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45 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Reversing Flows and Heat Spike: Caused by Solar g-Modes?

The Quasi Biennial Oscillation in the Earth s upper atmosphere has an analog deep inside the Sun. As on Earth, the flow is east or west, it is at low latitude, and it reverses direction in a roughly periodic manner. The period in the solar case is 1.3 years. It was detected using solar oscillations similar to the way earthquakes are used to study the Earth's interior. But its cause was not known. We showed that global oscillations (g-modes) can supply enough angular momentum to drive zonal flows with the observed reversal period. This required a calculation of wave dissipation rates inside each flow and in the turbulent layer that separates any two flows of opposite sign. Heat that this process leaves behind causes a thermal spike inside the Sun at the same depth. This may explain an anomaly in observed sound speed that has had no sure explanation.

Mayr, Hans G.↗
NASA NTRS1983

Tectonic deformation of the Andes and the configuration of the subducted slab in central Peru: Results from a micro-seismic experiment

The vast majority of the microearthquakes recorded occurred to the east: on the Huaytapallana fault in the Eastern Cordillera or in the western margin of the sub-Andes. The sub-Andes appear to be the physiographic province subjected to the most intense seismic deformation. Focal depths for the crustal events here are as deep as 50 km, and the fault plane solutions, show thrust faulting on steep planes oriented roughly north-south. The Huaytapallana fault in the Cordillera Oriental also shows relatively high seismicity along a northeast-southwest trend that agrees with the fault scarp and the east dipping nodal plane of two large earthquakes that occurred on this fault in 1969. The recorded microearthquakes of intermediate depth show a flat seismic zone about 25 km thick at a depth of about 100 km. This agrees with the suggestion that beneath Peru the slab first dips at an angle of 30 deg to a depth of 100 km and then flattens following a quasi-horizontal trajectory. Fault plane solutions of intermediate depth microearthquakes have horizontal T axes oriented east-west.

Suarez, G.↗
NASA NTRS2005

Offshore Breaking of Impact Tsunami: Van Dorn was Right

Tsunami generated by the impacts of asteroids and comets into the Earth s oceans are widely recognized as a potentially catastrophic hazard to the Earth s population (e.g. Chapman and Morrison 1994, Nature, 367, 33; Hills et al. 1994, in Hazards Due to Comets and Asteroids, (ed. T. Gehrels), 779; Atkinson et al. 2000, Report of the UK Task Force on Potentially Hazardous NEOs; Ward and Asphaug 2000, Icarus, 145, 64). A peculiarity of ocean impacts is the potential global effects of an impact that would otherwise be of only regional or local importance should it occur on land. This is, of course, due to the ability of waves to propagate globally, as seen by the terrible effects of the recent earthquake off the coast of Sumatra. The overall process of an impact tsunami is complex and falls into several distinct phases: 1) initial impact of the bolide into the ocean and formation of a transient cavity in the water, 2) collapse of the cavity and propagation of large waves from the impact center outward over deep water (typically several km in depth), 3) initial effects on wave amplitude as shallower water of the continental slope is reached ("wave shoaling"), possible breaking of waves in relatively shallow water (less than 100 m depth), on continental shelves, and 5) final contact of waves with the shore and their progression onto dry land ("run-up" and "run-in"). Here we report on numerical calculations (and semi-analytic theory) covering phases 3 and 4.

Korycansky, D. G.↗
NASA NTRS1989

Volcanic eruptions and solar activity

The historical record of large volcanic eruptions from 1500 to 1980 is subjected to detailed time series analysis. In two weak but probably statistically significant periodicities of about 11 and 80 yr, the frequency of volcanic eruptions increases (decreases) slightly around the times of solar minimum (maximum). Time series analysis of the volcanogenic acidities in a deep ice core from Greenland reveals several very long periods ranging from about 80 to about 350 yr which are similar to the very slow solar cycles previously detected in auroral and C-14 records. Solar flares may cause changes in atmospheric circulation patterns that abruptly alter the earth's spin. The resulting jolt probably triggers small earthquakes which affect volcanism.

Stothers, Richard B.↗
NASA NTRS1980

Focal mechanism of deep moonquakes

To elucidate the focal mechanism of deep moonquakes, S-wave polarizations of deep moonquake signals from the A(1) source region are analyzed. At station 12, where the available data are of the highest quality, the variation of polarization angle with the anomalistic phase of the moon indicates agreement with that expected from the focal mechanism model of Nakamura (1978). Focal mechanism solutions were derived for eight A(1) moonquakes assuming that moonquakes are, like earthquakes, caused by a shear fracture on a fault plane. The mechanism solutions generally indicate a nearly horizontal or almost vertical faulting. The slip directions estimated from the solutions are different from one another, again suggesting variation of focal mechanisms as a function of the tidal phase of the moon.

Koyama, J.↗
NASA NTRS1994

Site velocities before and after the Loma Prieta and Gulf of Alaska earthquakes determined from VLBI

We use geodetic data from Very Long Baseline Interferometry (VLBI) to determine the pre- and postseismic velocities of two sites. We then place limits on variations in interseismic strain buildup. The 1987 and 1988 Gulf of Alaska earthquakes (each Ms = 7.6) broke the Pacific plate interior. During the earthquakes the Cape Yakataga site moved 78 mm toward southwest. During the 1989 Loma Prieta earthquake (Ms = 7.1) the Fort Ord site moved 48 mm toward north. Baselines (a) from Fairbanks to Cape Yakataga and (b) from Mojave to Fort Ord change at nearly the same rate before and after the earthquakes. Postseismic transients, which we determine from differences between post- and preseismic rates, are minor: at Cape Yakataga the transient is 3 +/- 4 mm in a postseismic interval of 23 months, and at Fort Ord the transient is 6 +/- 5 mm in 21 months. The slip beneath the Loma Prieta rupture needed to generate the Fort Ord transient is 0.22 +/- 0.19 m, one-tenth the coseismic slip (2 m). We analyze elastic lithosphere-viscous asthenosphere models to determine that the characteristic time describing exponential decay in deep fault slip is longer than 6 years. The VLBI measurements are consistent with uniform interseismic strain buildup. They disagree with fast postseismic rates caused by an asthenosphere with very low viscosity.

Argus, Donald F.↗
NASA NTRSDate not supplied

MAGIC Mission Science and Applications Related to Cryosphere, Solid Earth and Neutral Atmosphere

The GRACE and GFO missions have revolutionised our understanding of mass movement at and below the surface of the Earth but they, nonetheless, have restrictions related to spatial and temporal resolution and instrument sensitivity that limits our ability to resolve certain processes. In this presentation we focus on the advances and capabilities that the proposed Mass change And Geosciences International Constellation (MAGIC) mission will deliver for cryosphere and solid Earth applications and will also consider the potential it will have for studying the neutral atmosphere. The time-varying gravity missions to date have had an effective spatial resolution of ~300 km, which is larger than the scale of any glacier or ice caps and larger than most catchments on the Greenland Ice Sheet. Even over Antarctica, the limited spatial resolution is a major limitation for regions such as the Antarctic Peninsula. Tectonic process, such as Earthquakes, volcanic activity and even viscous mantle flow can take place on scales smaller than can be resolved currently. The target resolution and accuracy for MAGIC over ice is 170 km at 2.6 mm/yr EWH over the long term and 250 km at 5.5 mm EWH at monthly resolution plus lower accuracy daily to weekly capabilities. We consider here what this means for understanding and observing ice mass exchange with the oceans and improving our ability to measure the manometric contribution to sea level rise. Based on similar targets, we also explore the improvements this offers for monitoring different types of solid Earth processes including geohazards, crustal evolution and deep interior properties and dynamics. We also consider what contributions MAGIC will be able to make to observations of thermosphere neutral density and related atmospheric parameters.

Jonathan Bamber↗
NASA NTRS1992

Fault identification using multidisciplinary techniques at the Mars/Uranus Station antenna sites

A fault investigation was performed at the Mars and Uranus antenna sites at the Goldstone Deep Space Communications Complex in the Mojave desert. The Mars/Uranus Station consists of two large-diameter reflector antennas used for communication and control of deep-space probes and other missions. The investigation included interpretation of Landsat thematic mapper scenes, side-looking airborne radar transparencies, and both color-infrared and black-and-white aerial photography. Four photolineaments suggestive of previously undocumented faults were identified. Three generally discrete morphostratigraphic alluvial-fan deposits were also recognized and dated using geomorphic and soil stratigraphic techniques. Fourteen trenches were excavated across the four lineaments; the trenches show that three of the photolineaments coincide with faults. The last displacement of two of the faults occurred between about 12,000 and 35,000 years ago. The third fault was judged to be older than 12,000 years before present (ybp), although uncertainty remains. None of the surface traces of the three faults crosses under existing antennas or structures; however, their potential activity necessitates appropriate seismic retrofit designs and loss-prevention measures to mitigate potential earthquake damage to facilities and structures.

Santo, D. S.↗
NASA NTRS2010

What if Things Get Worse? Really Grand Challenges for Modeling and Simulation in a Risky and Complex World or Modeling and Simulation for the "Greater Good"?

Today Modeling and Simulation-- ---as an important practice or industry or area of expertise ----- is at a complex crossroad - a sort of cyber-highway--where these complexities meet-technical, economic, environmental, geopolitical and cultural. They may converge or collide. Let's not kid ourselves. It is all too much for anyone person or organization Malcolm Gladwell said it. "We have constructed a world in which the potential for high tech catastrophe is embedded in the fabric of everyday life." We are surrounded by problems that scream at us from our television, Internet and social networks along with billboards and protest signs. We face not just high tech catastrophes but, also, landslides, earthquakes, tornados, floods and hurricanes and large-scale criminality. Evil, war, famine and pestilence have not gone away. It is all too much to think about. My friend, George Peabody, who taught me everything I know about power said that addressing such issues requires that we constantly build our network, information resources and the credibility and visibility of our work. That is how we will build the power of simulation so it can change the world --even maybe, save it. We need all the help we can get and give one another because our human early warning systems appear to be out of kilter. We seem to have trouble imagining how small failings can continue to lead to catastrophic disaster. Think about O-rings and blowout preventers. One is reminded of the old nursery rhyme, "For want of a nail, a shoe was lost! for want of a shoe the horse was lost! for want of a rider the battle was lost and so the kingdom fell." Although the investigation will take more time for real answers, it is worrisome that a rig worker reported to the BBC that-- weeks before the explosion of Deep Ocean Horizon. -he identified a leak in the oil rig's safety equipment -the Control Pod of the blowout preventer which has giant shears designed to cut and seal off the well's main pipe. With both electronics and hydraulics, these are effectively the brains of the blowout preventer. No one fixed it, he alleges, they just shut it down and relied on the other control pod -an act deemed unacceptable by petroleum expert, Tad Patzek, at the University of Texas. The US Congress has identified numerous other problems with the blowout preventer, including design problems and unexpected modifications.

Fifrey, Priscilla↗