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At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Ultraviolet observations of beta Canis majoris and beta Cephei

Ultraviolet spectra of the two variables exhibit periodic variations in the H I, Si IV, and C IV resonance lines. Later scans of the beta Cep atmosphere show that the C IV line disappeared for short periods. Three possible mechanisms for this effect are: a beat phenomenon, shock waves, or tidal distortions. It is concluded that a tidal distortion is possible if the period of revolution is 12 days and if the inclination is sufficiently small to keep one tidal bulge out of sight and large enough to keep the secondary from eclipsing the primary bulge.

Fischel, D.↗
NASA NTRS1972

Monitoring changing geologic features along the Texas Gulf Coast

The author has identified the following significant results. Water truth observations, NASA aerial photography from an altitude of 60,000 feet, and ERTS-1 imagery made off the South Texas coast showed a mutually consistent pattern of water turbidity in the Gulf of Mexico. At the time of the measurements, plumes of turbid water were being formed by ebb-tidal discharges from the bays through tidal passes and were being diverted southward by the coastwise drift. The occurrence of the bands of turbid and relatively clear water suggests the existence of large scale helical circulation cells having axes almost parallel to shore with the outer turbid band probably being a zone of surface divergence and bottom water upwelling. The impingement of a turbid water mass onto the shoreline suggests that some, and perhaps most, of the suspended sediment in nearshore waters may not have been stirred up from the nearshore sea floor but may have traveled long distances in the water mass, perhaps even having remained in suspension from the time of its entry into the Gulf tidal inlets such as Aransas Pass.

Hunter, R. E.↗
NASA NTRS1972

Galactic bridges and tails.

This paper argues that the bridges and tails seen in some multiple galaxies are just tidal relics of close encounters. These consequences of the brief but violent tidal forces are here studied in a deliberately simple-minded fashion. Each encounter is considered to involve only two galaxies and to be roughly parabolic; each galaxy is idealized as just a disk of noninteracting test particles which initially orbit a central mass point. As shown here, the two-sided distortions provoked by gravity alone in such circumstances can indeed evolve kinematically into some remarkably narrow and elongated features. Besides extensive pictorial survey of tidal damage, this paper offers reconstructions of the orbits and outer shapes of four specific interacting pairs: Arp 295, M51 + NGC 5195, NGC 4676, and NGC 4038/9.

Toomre, A.↗
NASA NTRS1972

Comments on lunar origin.

Consideration of the tidal evolution of the earth-moon system in the light of recent published studies of lunar origin. The subjects include the factors of orbital evolution, the auxiliary Model Zero, orbital evolution along the outgoing branch, capture models, capture probability, capture with break-up, the tidal evolution of circular and elliptical fragmented rings, and precession and collisions in a ring of fragments. A numerical integration of precessions is performed for the actual nonzero mass of the moon and for a lunar distance of about 22 earth radii. A simplified Model Zero is found to compare well with Goldreich's solution (1968). It is concluded that the moon must have become freely yielding to tidal deformation at distances less than about 8 earth radii. Arguments are given in favor of the capture theory as a basis for the genesis of the moon.

Opik, E. J.↗
NASA NTRS1973

Sea, ice and surface water circulation, Alaskan continental shelf

The author has identified the following significant results. ERTS-1 imagery has been extremely useful in understanding the tidal water movements in a large estuary such as Cook Inlet. As more imagery obtained during various tidal stages become available it appears that complex and fast changing micro-circulation patterns develop in various regions of Cook Inlet during each advancing and receding tide. More ERTS-1 synoptic imagery is needed to fully understand the effect of the approach of tidal front on the water movements in the various regions through the estuary. The conventional onboard ship data gathered during various cruises although revealed the overall circulation pattern in Cook Inlet but failed to show micro-subgyres which develop in various regions during each tide which are discernible on ther ERTS-1 imagery. Suspended load distribution in the Bering Sea during summer varies significantly. In areas of phytoplankton bloom and at the river mouths the suspended load is higher than the 1 mg/1 which is found over most areas. The influence of major rivers on temperature, salinity, and suspended load in surface water as well as at shallow depth is apparent. On the Bering shelf a strong pycnocline generally at depth 10-20 m is formed by surface fresh water flow which retains sediment in suspension over extended periods.

Sharma, G. D.↗
NASA NTRS1973

Monitoring coastal water properties and circulation from ERTS-1

The author has identified the following significant results. Imagery and digital tapes from nine successful ERTS-1 passes over Delaware Bay during different portions of the tidal cycle have been analyzed with special emphasis on turbidity, current circulation, waste disposal plumes, and convergent boundaries between different water masses. ERTS-1 image radiance correlated well with Secchi depth and suspended sediment concentration. MSS band 5 seemed to give the best representation of sediment load in the upper one meter of the water column. Circulation patterns observed by ERTS-1 during different parts of the tidal cycle, agreed well with predicted and measured currents throughout Delaware Bay. During flood tide the suspended sediment as visible from ERTS-1 also correlated well with the depth profile. Convergent shear boundaries between different water masses were observed from ERTS-1, with foam lines containing high concentrations of lead, mercury, and other toxic substances. Several fronts have been seen. Those near the mouth of the bay are associated with the tidal intrusion of shelf water. Fronts in the interior of the bay on the Delaware side appear to be associated with velocity shears induced by differences in bottom topography. Waste disposal plumes have benn detected 36 miles offshore.

Klemas, V.↗
NASA NTRS1974

Moonquake predetermination and tides

A pattern in moonquakes, which correlates with the monthly tidal cycle, also correlates with a phase-shifted pattern of a 7-month tidal cycle. The lead of approximately 2 months in moonquake occurrence can be explained if local tidal forces are combined with a moonquake-driving force. This force, assumed to result from the 6-yr physical libration in latitude, would cause N-S sliding of an outer layer across a solid layer within a decoupled core in a lunar model. During 1969-1971, the sliding would be southward with a progression of monthly maxima in the combined forces. Where these forces control moonquakes, the reversal in direction of the 6-year cyclic force in early 1972 should cause a minimum in moonquake activity. Decreases toward such a minimum did occur simultaneously in the similar progressions of monthly moonquakes and maxima in the combined forces at the most active hypocenter. Repetition of the 1966-1971 force pattern in 1975-1977 should produce a corresponding repetition of the moonquake pattern.

Chapman, W. B.↗
NASA NTRS1975

On the planetary theory of sunspots

An investigation is conducted of the full tidal problem for Mercury, Venus, Earth, and Jupiter, the tide-raising planets, taking into account the complete orbital elements, including eccentricity, inclination, and their variation with time. Data for a comparison of tidal and sunspot dates are listed in a table. The investigation shows that the alignment of the tide-raising planets within 10 degrees is a common phenomenon, occurring approximately every 10.4 years. This alignment is not associated with drastic tidal effects.

Okal, E.↗
NASA NTRS1976

Diurnal tide in the Martian atmosphere

Classical atmospheric tidal theory is extended to include the effects of large-amplitude planetary-scale variations of the terrain height. Utilizing simple models of the thermotidal forcing, the resulting technique is used to compute the diurnal tide in both the dust-free and the dust-laden Martian atmosphere. The main effect of the Martian variable terrain is to drive topographic tidal modes which can propagate vertically and to excite the possibly resonant diurnal Kelvin mode. The resulting surface wind can exceed 20 m/sec and may determine the preferred location for the initiation of global dust storms. In the middle Martian atmosphere (30-80 km) static and shear instabilities embedded within the tidal fields will generate extensive, though variable, regions of turbulence. Vertical mixing by this turbulence and transport by the tide itself may help to stabilize the middle Martian atmosphere against photolysis.

Zurek, R. W.↗
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. Solutions for M2, S2, N2, K2, K1, O1, P1 tidal constituents neglecting the effects of ocean loading and self-gravitation and a converged M2, solution including ocean loading and self-gravitation effects are presented in the form of cotidal and corange maps.

Estes, R. H.↗
NASA NTRS1977

On the evolution of the lunar orbit

It is generally accepted that the earth-moon separation is at present increasing due to tidal dissipation. Values for the corresponding lunar deceleration and the related slowing of the earth's rotation are obtained from astronomical observations and studies of ancient eclipses. Extrapolation of these values leads to a close approach of the earth and moon 1-3 b.y. BP. Periodicities in the Precambrian stromatolites may yield the number of solar days in a lunar month prior to 500 m.y. BP. These data combined with dynamic constraints on the number of solar days in a lunar month indicate a close approach of the earth and moon at 2.85 plus or minus 0.25 b.y. BP. Mare volcanism on the moon and high-temperature Archean volcanism on the earth prior to this date may be due to tidal heating. Strong tidal heating during a close approach could have contributed to the formation of the first living organisms.

Turcotte, D. L.↗
NASA NTRS1977

Lunar seismicity and tectonics

Results are presented for an analysis of all moonquake data obtained by the Apollo seismic stations during the period from November 1969 to May 1974 and a preliminary analysis of critical data obtained in the interval from May 1974 to May 1975. More accurate locations are found for previously located moonquakes, and additional sources are located. Consideration is given to the sources of natural seismic signals, lunar seismic activity, moonquake periodicities, tidal periodicities in moonquake activity, hypocentral locations and occurrence characteristics of deep and shallow moonquakes, lunar tidal control over moonquakes, lunar tectonism, the locations of moonquake belts, and the dynamics of the lunar interior. It is concluded that: (1) moonquakes are distributed in several major belts of global extent that coincide with regions of the youngest and most intense volcanic and tectonic activity; (2) lunar tides control both the small quakes occurring at great depth and the larger quakes occurring near the surface; (3) the moon has a much thicker lithosphere than earth; (4) a single tectonic mechanism may account for all lunar seismic activity; and (5) lunar tidal stresses are an efficient triggering mechanism for moonquakes.

Lammlein, D. R.↗
NASA NTRS1978

Continuous distributions of specific ventilation recovered from inert gas washout

A new technique is described for recovering continuous distributions of ventilation as a function of tidal ventilation/volume ratio from the nitrogen washout. The analysis yields a continuous distribution of ventilation as a function of tidal ventilation/volume ratio represented as fractional ventilations of 50 compartments plus dead space. The procedure was verified by recovering known distributions from data to which noise had been added. Using an apparatus to control the subject's tidal volume and FRC, mixed expired N2 data gave the following results: (a) the distributions of young, normal subjects were narrow and unimodal; (b) those of subjects over age 40 were broader with more poorly ventilated units; (c) patients with pulmonary disease of all descriptions showed enlarged dead space; (d) patients with cystic fibrosis showed multimodal distributions with the bulk of the ventilation going to overventilated units; and (e) patients with obstructive lung disease fell into several classes, three of which are illustrated.

Lewis, S. M.↗
NASA NTRS1979

Applications of HCMM data to soil moisture snow and estuarine current studies

The author has identified the following significant results. Additional analyses of Luverne, Minnesota ground data revealed that soil moisture variations are independent of elevation effects. Tidal fluctuations in the Potomac River and Delaware Bay were examined as a function of surface temperature. Preliminary findings suggest that temperature boundaries are sufficient to detect various stages of the tidal cycle in Delaware Bay, but are as yet uncertain for prediction in the Potomac River. At least three additional cases are needed to completely evaluate the tidal cycle. An alphanumeric printout at a scale of 1:1,000,000 compares closely with a 1:1,000,000 scale DMD image of the Chesapeake Bay region.

Wiesnet, D. R.↗
NASA NTRS1979

Global Earth Response to Loading by Ocean Tide Models

Mathematical and programming techniques to numerically calculate Earth response to global semidiurnal and diurnal ocean tide models were developed. Global vertical crustal deformations were evaluated for M sub 2, S sub 2, N sub 2, K sub 2, K sub 1, O sub 1, and P sub 1 ocean tide loading, while horizontal deformations were evaluated for the M sub 2 tidal load. Tidal gravity calculations were performed for M sub 2 tidal loads, and strain tensor elements were evaluated for M sub 2 loads. The M sub 2 solution used for the ocean tide included the effects of self-gravitation and crustal loading.

Estes, R. H.↗
NASA NTRS1979

Evidence for vertical motions in the equatorial middle atmosphere

The Diurnal Experiment, which took place in March 1974, offers a unique data set for use in studying vertical velocities in the equatorial stratosphere and mesosphere. Application of the standard thermodynamic vertical velocity equation along with a generalized thermal wind relation reveals magnitudes of vertical velocities ranging from 1-2 cm/s in the lower stratosphere to 10-15 cm/s in the lower mesosphere. Diurnal and semidiurnal tidal modes are quite apparent and, in agreement with tidal theory, the amplitudes of the oscillations increase with height. Inspection of time cross sections and use of Fourier analysis indicates vertical wavelengths on the order of 8-16 km. These results suggest that modification of temperature and wind profiles in the stratosphere and lower mesosphere on an hourly basis can be quite significant. The analysis also suggests the presence of unresolved vertical winds on both longer and shorter time scales than the principal tidal components.

Weisman, M. L.↗
NASA NTRS1980

Thermal Pollution Mathematical Model: Verification of Three-Dimensional Free-Surface Model at Anclote Anchorage - Volume 6

The free-surface model presented is for tidal estuaries and coastal regions where ambient tidal forces play an important role in the dispersal of heated water. The model is time dependent, three dimensional, and can handle irregular bottom topography. The vertical stretching coordinate is adopted for better treatment of kinematic condition at the water surface. The results include surface elevation, velocity, and temperature. The model was verified at the Anclote Anchorage site of Florida Power Company. Two data bases at four tidal stages for winter and summer conditions were used to verify the model. Differences between measured and predicted temperatures are on an average of less than 1 C.

Lee, S. S.↗
NASA NTRS1980

Detection of tides on the Patagonian shelf by the SEASAT satellite radar altimeter - An initial comparison

The detection of tides on the Patagonian shelf off Argentina by the SEASAT satellite radar altimeter is reported. The satellite data was obtained during two passes of the satellite over the shelf on August 1 and August 4, 1978, and compared with empirical estimates of the tidal elevation along the satellite ground tracks based on coastal tide gage data, an estimate of tidal variation over the shelf, and the tidal prediction equations of Shureman (1958). Good agreement was observed between the satellite data of sea surface height with respect to a standard ellipsoid and the empirical estimate for the near-shore pass, with agreement degraded slightly for the pass further off shore. It is concluded that the generally good agreement found demonstrates the applicability of satellite radar altimeter data to the determination of tides and that small length scale fluctuations in the geoid are minor along the two ground tracks.

Parke, M. E.↗