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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

A computer software system for the generation of global ocean tides including self-gravitation and crustal loading effects

A computer software system is described which computes global numerical solutions of the integro-differential Laplace tidal equations, including dissipation terms and ocean loading and self-gravitation effects, for arbitrary diurnal and semidiurnal tidal constituents. The integration algorithm features a successive approximation scheme for the integro-differential system, with time stepping forward differences in the time variable and central differences in spatial variables.

Estes, R. H.↗
NASA NTRS1977

Planetary tides during the Maunder Sunspot Minimum

In order to test the tidal theory of sunspots, sun-centered planetary conjunctions and tidal potentials are reconstructed for the period of the Maunder Minimum (1645 to 1715). These are found to be effectively indistinguishable from patterns of conjunctions and power spectra of tidal potential in the modern era of a well-established 11-yr sunspot cycle. The pattern of planetary tidal forces during the Maunder Minimum is then reconstructed to investigate the possibility that multiple-planet forces were somehow fortuituously cancelled at that time; i.e., the positions of the slower moving planets in the late 17th and early 18th centuries were such that conjunctions and tidal potentials were reduced in number and force. Calculations of daily positions for Mercury, Venus, earth, and Jupiter as well as daily values of the tidal potential for the period from 1450 to 2000 indicate no striking dissimilarities between the time of the Maunder Minimum and any other period considered.

Smythe, C. M.↗
NASA NTRS1978

Open ocean tide modelling

Two trends evident in global tidal modelling since the first GEOP conference in 1972 are described. The first centers on the incorporation of terms for ocean loading and gravitational self attraction into Laplace's tidal equations. The second centers on a better understanding of the problem of near resonant modelling and the need for realistic maps of tidal elevation for use by geodesists and geophysicists. Although new models still show significant differences, especially in the South Atlantic, there are significant similarities in many of the world's oceans. This allows suggestions to be made for future locations for bottom pressure gauge measurements. Where available, estimates of M2 tidal dissipation from the new models are significantly lower than estimates from previous models.

Parke, M. E.↗
NASA NTRS1978

Body tides on an elliptical rotating earth

The complete tidal response of an elliptical, rotating, elastic Earth is found to contain small displacements which do not fit into the conventional Love number framework. Corresponding observable tidal quantities (gravity, tilt, strain, Eulerian potential, etc.) are modified by the addition of small latitude dependent terms.

Wahr, J. M.↗
NASA NTRS1981

The changing tide: Federal support of civilian-sector R and D

The involvement of the Federal government in civilian sector research and development is discussed. Relevant policies are put in an historical perspective. The roles played by industrial research and public funding are reveiwed. Government support of basic an generic research, clientele-oriented applied research, and research with commercial ends is studied. Procurement, anti-trust, and patent policies, all of which affect the climate for private research and development, are examined.

Fusfeld, H. I.↗
NASA NTRS1981

Analyze satellite-tracking laser data in order to study satellite ephemerides, solid-Earth and ocean tides and laser system performance

The decrease in the semimajor axis of Lageos is considerably larger than expected. Gravitational effects, reference system effects, solar radiation pressure, Earth albedo pressure, neutral atmospheric drag, the Poynting Robertson Effect, and electrodynamic effects were used in explaining the observations. Quick look data provided are used to determine the Earth's polar motion and length of day. This process is routine, and provides these geophysical data every five days.

Gaposchkin, E. M.↗
NASA NTRS1981

Dissipation due to obliquity-induced tides in a Kelvin-Voigt viscoelastic body

A calculation is conducted regarding the local and total dissipation rate of mechanical energy for an incompressible, Kelvin-Voigt body in a circular orbit with finite obliquity. The considered material is characterized by a shear modulus and a viscosity. Of the two parameters, only the shear modulus is known. An investigation is conducted regarding the variation of the total dissipation rate with viscosity. For small values of the viscosity the Kelvin-Voigt material approximates the behavior of an elastic solid. In this range, results for the earth-moon system are similar to those obtained by Peale and Cassen (1978) using a modified form of the elastic solution. For large values of the viscosity the results are qualitatively different from those in the 'elastic' range, as viscous effects dominate the material response.

Vanarsdale, W. E.↗
NASA NTRS1981

Effect of the fluid core on changes in the length of day due to long period tides

The long period luni-solar tidal potential is known to cause periodic changes in the earth's rotation rate. It is found that the effect of a dissipationless fluid outer core is to reduce the amplitudes of these tidal perturbations by about 11 percent. When the fluid core effect is added to Agnew and Farrell's (1978) estimate of the effect of an equilibrium ocean, the result is in accord with observation. The effects of dissipative processes within the fluid core are also examined. Out-of-phase perturbations are found which could be as large as about 10 ms at 18.6 yr. It is concluded, however, that the poorly understood decade fluctuations in the earth's rotation rate will prohibit observation of this effect.

Wahr, J. M.↗
NASA NTRS1983

Atmospheric tides on Venus. III - The planetary boundary layer

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Dobrovolskis, A. R.↗
NASA NTRS1984

Some Aspects of General Circulation and Tides in the Middle Atmosphere

Data from several sources suggest that between 100 and 200 km in the middle atmosphere, a layer of anomalous circulation must be situated, at least in middle latitudes. The mechanisms responsible for the circulation anomaly in this height region are discussed in terms of hydrodynamic equations. The current state of atmospheric tidal theory is also addressed.

Ivanovskiy, A. I.↗
NASA NTRS1985

Atmospheric Tides Below 80 Km

Measurements of diurnal and semidiurnal tidal oscillations between about 25 and 80 km are reviewed. At latitudes greater than about 30 deg, S to N wind components are consistently in quadrature with and similar to the W to E components. The tidal structures are interpreted as a superposition of quasi-steady higher order modes excited in the troposphere by sources of limited extent (approx. 1,000 km). At latitudes less than about 30 deg, steady or quasi-steady diurnal and semidiurnal components are not necessarily the dominant components of daily variation. At high latitudes diurnal phases generally show little change with height in comparison with observations at lower latitudes in accord with the latitudinal properties of positive and negative diurnal modes.

Forbes, J. M.↗
NASA NTRS1985

Data Descriptions and Vertical Structure Plots for Mean, Diurnal, and Semidurnal Components of Eastward and Northward (ordered by Latitude). Mean Winds and Tides over Poker Flat, Alaska (65 Deg N, 147 Deg W), During November 1981

The mean zonal and meridional winds and the amplitude and phase structures for the tidal harmonics for the month of November, 1981 are given. The mean winds are weak westerlies and weak southerlies. The westerlies are approximately 10 ms (-1) lower than those during November 1980 and 1982. The diurnal amplitudes are small in both the zonal and meridional wind components. The diurnal phase structures are characteristic of a propagating wave having a ertical wavelength of approximately 50 km. The semidiurnal tidal harmonic amplitudes are slightly larger than the diurnal amplitudes. However, the phase structures are different for the zonal and meridional components. The meridional phase structure appears evanescent. The zonal phase structure has a phase reversal at 88 km with downward phase progression below that level and upward phase progression above that level. The vertical wavelength is roximately 12 km. This short vertical wavelength occurs during other months of the year but longer wavelengths are more common.

Avery, S. K.↗
NASA NTRS1985

Mean Winds and Tides over Urbana, Illinois During November 16-22, 1981

The Urbana Meteor Radar uses a high power pulse transmitter to achieve high echo rates, and an interferometer to spatially locate the individual echoes. The irregularly spaced observations of range, radial velocity, and direction cosines are reduced to a rectangular grid, evenly spaced in time and height, of estimates of the zonal and meridional wind. This is accomplished using the method of GROVES whereby a constant horizontal wind is fitted, using least squares, to all echoes occurring within a fixed time/height interval. This interpolation region is then stepped in time and height. the size of the interpolation region is 2 hours by 5 km, the time step is approximately 11 minutes, and the height step is 2 km. The filtering of high temporal and spatial frequencies is somewhat reduced by weighting the echoes according to their distance from the center of the interpolation box.

Tetenbaum, D.↗
NASA NTRS1986

Geodesy by radio interferometry - Determinations of baseline vector, earth rotation, and solid earth tide parameters with the Mark I very long baseline radio interferometery system

Thirty-seven very long baseline radio interferometry experiments performed between 1972 and 1978 are analyzed and estimates of baseline vectors between six sites, five in the continental United States and one in Europe are derived. No evidence of significant changes in baseline length is found. For example, with a statistical level of confidence of approximately 85 percent, upper bounds on such changes within the United States ranged from a low of 10 mm/yr for the 850 km baseline between Westford, Massachusetts, and Green Bank, West Virginia, to a high of 90 mm/yr for the nearly 4000 km baseline between Westford and Goldstone, California. Estimates for universal time and for the x component of the position of the earth's pole are obtained. For the last 15 experiments, the only ones employing wideband receivers, the root-mean-square differences between the derived values and the corresponding ones published by the Bureau International de l'Heure are 0.0012 s and 0.018 arc sec respectively. The average value obtained for the radial Love number for the solid earth is 0.62 + or - 0.02 (estimated standard error).

Ryan, J. W.↗