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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Is regolith absorbtion the explanation for the transition from early to present Mars climate

Experimental data is presented for CO2 adsorption on palagonites (now thought to provide the most acceptable spectral match to Mars weathering products). When corrected for great differences in specific surface area, the adsorptive behavior exhibited by palogonites, nontronite, and basalt with respect to CO2 can be (approx.) described by the same generic equation. Using this relationship normalized to a Mars soil surface area, and the dependence of subsurface temperatures on latitude and depth, the current inventory of regolith absorbed CO2 was estimated.

Fanale, F. P.↗
NASA NTRS1988

A possible explanation for the inconsistency between the Giotto grain mass distribution and ground-based observations

Giotto measured the in situ Halley dust grain mass distribution with 2 instruments, Particle Impact Analyzer and Dust Impact Detection System (DIDSY), as well as the total intercepted mass from the deceleration of the spacecraft (Giotto Radio-Science Experiment, GRE). Ground based observations made shortly before encounter have fluxes much higher than would be predicted from Giotto data. It is concluded that Giotto DIDSY and GRE data represent observations of dust originating from a narrow track along the nucleus. They are consistent with ground based data, if assumptions are made about the level of activity along this track. The actual size distribution that should be used for modeling of the whole coma should not include the large mass excess actually observed by Giotto. Extrapolation of the small grain data should be used, since for these grains the velocity dispersion is low and temporal changes at the nucleus would not affect the shape of the mass distribution.

Perry, C. H.↗
NASA NTRS1988

Possible explanations of north-south plasma flow in the outer heliosphere and meridional transport of magnetic flux

Observed meridional plasma flow and its connection with other plasma parameters in the outer heliosphere are discussed. The dynamics of the flow are examined locally and compared with observed plasma parameters and a global flow model which predicts such flows in a steady solar wind. The observational evidence supports stream dynamics and associated pressure gradients as responsible for driving the flow. Such a meridional flow may result in a net transport of magnetic flux from regions near the heliographic equator. The amplitude of the observed meridional component of solar wind flow is consistent with observed magnetic flux deficits in the outer heliosphere. The limited coverage of heliographic latitude by Voyager 2 precludes a direct measurement of the full flow pattern; however, the magnitude of reported magnetic flux deficits and the unambiguous, regular variations in the meridional flow suggest that the stream interactions do produce a net movement of magnetic flux away from the heliographic equator.

Mcnutt, R. L., Jr.↗
NASA NTRS1989

Tidal evolution of the Uranian satellites. II - An explanation of the anomalously high orbital inclination of Miranda

It is proposed that the current, anomalously high orbital inclination of the Uranian satellite, Miranda, can be accounted for by temporary capture into the 3:1 resonance with Umbriel. This would imply that the orbits of the satellites have tidally evolved sufficiently to have permitted passage through this resonance. Escape from resonance is suggested to have occurred by way of a novel dynamical mechanism, in which the trajectory encounters low-order commensurabilities between the libration frequency of the resonant argument and other fundamental system frequencies.

Tittemore, William C.↗
NASA NTRS1989

Ions in grain mantles - A new explanation for the 6.86 micron absorption in W33A

The 6.86-micron absorption in W33A has been investigated using the results of laboratory experiments simulating the photochemistry of interstellar grain mantles. The 5-8-micron IR spectrum, and particularly the 6.86-micron absorption, of W33A can be reproduced with ultraviolet irradiated water-rich ices. The 5-8-micron spectrum of W33A exhibits effects which are interpreted as due to dust material heated to different temperatures along the line of sight. Photolyzed dust mantles with a temperature less than 100 K provide the 6.0-micron absorption, while dust mantles heated to more than 100 K are the main contributors to the 6.86-micron absorption feature. Different photolysis and heating scenarios, as well as line of sight effects, are required to account for the 5-8-micron spectra of other protostellar objects.

Grim, Ruud J. A.↗
NASA NTRS1990

An explanation for the rise in T(sub c) in the Tl- and Bi-based high temperature superconductors

Using the plasmon exchange model for the high T(sub c) superconductor, it is shown that the T(sub c) rises with an increase in the number of CuO layers per unit cell, which is in agreement with recent observations in the Tl- and Bi-based compounds. The calculation also suggests that the sample will become superconducting in successive stages and that there is a saturation effect, i.e., that T(sub c) cannot be raised indefinitely by increasing the number of CuO layers.

Bose, S. M.↗
NASA NTRS1989

Implications of AAOE observations for proposed chemical explanations of the seasonal and interannual behavior of Antarctic ozone

Model simulations were used to investigate the seasonal and interannual behavior of ozone for different choices of initial odd nitrogen concentration in July and different assumptions on the heterogeneous reactions, with particular consideration given to the possible contribution of chlorine chemistry to the ozone hole phenomenon. The numerical experiments were selected based on the simulations of the observed trace gas concentrations during the Airborne Antarctic Ozone Experiment in 1987. In all cases considered, the catalytic cycle associated with the formation and photolysis of Cl2O2 could account for more than half of the photochemical removal of O3 within the Antarctic vortex through mid-September. The reaction of BrO with ClO, which accounts for 15-20 percent of O3 removal in the same period, tends to play a more important role toward the end of September, when the concentration of ClO is expected to decrease. No simple relationship was found between the increase in chlorine lavel and the interannual decrease in Antarctic O3.

Ko, M. K. W.↗
NASA NTRS1990

Right-lateral shear and rotation as the explanation for strike-slip faulting in eastern Tibet

Bounds are placed here on the rate of rotation proposed by Cobbold and Davy (1988) for the major strike-slip faults in the eastern Tibetan Plateau. It is also concluded here that the image of lateral transport on such faults, known also as continental escape, extrusion, or expulsion, is an illusion, and that instead the left-lateral slip on east-striking plates in eastern Tibet is a manifestation of north-striking right-lateral simple shear. If this conclusion is correct, the east-striking left-lateral faults and the crustal blocks between them are rotating clockwise at 1-2 deg/Myr, the east-west dimension of eastern Tibet is shortening at 10-20 mm/yr, and little material is moving eastward out of India's path into Eursasia by left-lateral simple shear.

England, Philip↗
NASA NTRS1990

Vertical distribution of water in the atmosphere of Venus - A simple thermochemical explanation

Several lines of evidence concerning the vertical abundance profile of water in the atmosphere of Venus lead to strikingly unusual distributions (the water vapor abundance decreases sharply in the immediate vicinity of the surface) or to serious conflicts in the profiles (different IR bands suggest water abundances that are discrepant by a factor of 2.5 to 10). These data sets can be reconciled if (1) water molecules associate with carbon dioxide and sulfur trioxide to make gaseous carbonic acid and sulfuric acid in the lower atmosphere, and (2) the discrepant 0.94-micrometer water measurements are due to gaseous sulfuric acid, requiring it to be a somewhat stronger absorber than water vapor in this wavelength region. A mean total water abundance of 50 + or - 20 parts/million and a near-surface free water vapor abundance of 10 + or - 4 parts/million are derived.

Lewis, John S.↗
NASA NTRS1991

A dynamical explanation for the asymmetry in zonally averaged column abundances of ozone between northern and southern springs

The observed zonally averaged column ozone shows a maximum at 90 deg N during the northern winter and spring and at 60 deg S throughout the southern winter and spring. This asymmetry is explained in the context of a zonally averaged model with coupled radiation, dynamics, and chemistry, together with consistently parameterized planetary wave driving and wave transport. It is shown that in the presence of weak wave driving, the penetration of the tropospheric circulation into the lower stratosphere and the characteristics of ozone chemistry are such that they produce a column ozone maximum at subpolar latitudes. The effect of increased wave driving is to intensify the residual circulation and extend it farther poleward, resulting in an ozone maximum at the pole. The role of the mesospheric drag is to further enhance these column ozone maxima. Model calculations show that the positions of the observed column ozone maxima are consistent with intensities of wave driving in the two hemispheres derived from data.

Hou, Arthur Y.↗
NASA NTRS1991

An explanation for Neptune's ring arcs

The Voyager mission revealed a complex system of rings and ring arcs around Neptune and uncovered six new satellites, four of which occupy orbits well inside the ring region. Analysis of Voyager data shows that a radial distortion with an amplitude of approximately 30 kilometers is traveling through the ring arcs, a perturbation attributable to the nearby satellite Galatea. Moreover, the arcs appear to be azimuthally confined by a resonant interaction with the same satellite, yielding a maximum spread in ring particle semimajor axes of 0.6 kilometer and a spread in forced eccentricities large enough to explain the arc's 15-kilometer radial widths. Additional ring arcs discovered in the course of this study give further support to this model.

Porco, Carolyn C.↗
NASA NTRS1991

An explanation for the rise in Tc in the Tl- and Bi-based high temperature superconductors

Using the plasmon exchange model for the high T(sub c) superconductor, it is shown that the T(sub c) rises with an increase in the number of CuO layers per unit cell, which is in agreement with recent observations in the Tl- and Bi-based compounds. The calculation also suggests that the sample will become superconducting in successive stages and that there is a saturation effect, i.e., that T(sub c) cannot be raised indefinitely by increasing the number of CuO layers.

Bose, S. M.↗
NASA NTRS1991

An explanation for both the large inclination and eccentricity of the dipole-like field of Uranus and Neptune

It is shown that the offset tilted dipole model of Uranus and Neptune, deduced from the spherical harmonic analysis of the Voyager magnetic field observation, can be represented fairly well by the combined field of an axial and an auxiliary dipole; the latter is roughly oriented in the east-west direction and is located near the surface of the core in low latitude. The present dynamo theories of planetary magnetism consider an axial dipolar field as an essential element, since the planetary rotation plays a vital role in the dynamo process. On the other hand, the auxiliary dipoles may be a result of leakage of the toroidal field, like a pair of sunspots on the photosphere, which is also an essential part of the dynamo process.

Akasofu, S.-I.↗
NASA NTRS1992

A weakly nonlinear theory based explanation for wave interactions in rotating channel flow

A weakly nonlinear wave-interaction theory is used to explain the decay of linearly unstable oblique waves in rotating channel flow at low Reynolds number. At the low Reynolds number studied, the waves tend to stabilize each other and therefore when no waves are preferentially excited, the linearly most unstable mode reaches a nonlinear amplitude first and causes the stabilization of all competing modes.

Singer, Bart A.↗
NASA NTRS1992

Possible explanations of the large angle fluctuations of the microwave background

Possible origins of the structure in the cosmic microwave background radiation are discussed. It is pointed out that the presence of such structure is compatible with the 1990 modified steady state model proposed by Arp et al. The possibility that the fluctuations are due to dust grains in the form of iron whiskers produced comparatively locally is also discussed.

Hoyle, F.↗