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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 1,459 records · Page 81
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NASA NTRS1972

Analyses of solar viewing time, beta angle, and doppler shift for solar observations from the space shuttle

Studies of solar physics phenomena are aided by the ability to observe the sun from earth orbit without periodic occultation. Charts are presented for the selection of suitable orbits about the earth at which a spacecraft is continuously illuminated through a period of a few days. Selection of the orbits considers the reduction of Doppler shift and wavefront attenuation due to relative orbital velocity and residual earth atmosphere.

Brandon, J. P.↗
NASA NTRS1972

Observation of solar particle fluxes over extended solar longitudes.

Detailed particle observations from various Pioneer spacecraft located at different heliolongitudes during the complex solar flare events of Mar. 30 to Apr. 10, 1969, have been utilized to investigate the energy dependence of azimuthal gradients of cosmic ray particles and its effect on the decay of the flare intensity. For an observer located to the east of the centroid of the population, the azimuthal corotation term and the convection term will be additive, resulting in a short decay time constant. An observer located to the west of the centroid of the population will experience a much longer decay time constant, the corotation term partially or completely compensating the loss of particles due to convection. At very low energies, the azimuthal corotation term may even be more than the convection term, thus resulting in a rise in intensity instead of decay during the later part of the event.

Bukata, R. P.↗
NASA NTRS1973

Photospheric faculae and the solar oblateness - A reply to 'Faculae and the solar oblateness' by R. H. Dicke.

Dicke has recently contested our statement in an earlier paper that faculae could account for a large part, if not all, of the solar oblateness signal measured by Dicke and Goldenberg in 1966. Using the facular oblateness signal published in our earlier paper and some hitherto unpublished data from his 1966 observations, he concludes that faculae account for only a small part (11%) of the observed excess oblateness. His analysis considers data only from a restricted 48-day sample and is based on the assumption that only the observed oblateness signal is subject to error. Our analysis considers data from all 64 days on which observations were made, and is based on the assumption that both the observed oblateness signal and the facular signal are subject to error. We find that faculae account for at least one-third to one-half of the observed excess oblateness, depending on whether 48 days or 64 days are used in the analysis.

Chapman, G. A.↗
NASA NTRS1975

Comments on the course of solar activity during the declining phase of solar cycle 20 /1970-74/

Observational data on sunspots, the 2800-MHz flux, and calcium plages are interpreted which were obtained during the declining phase of solar cycle 20. It is shown that three pulses of activity occurred during this period and resulted in two conspicuous 'stillstands' in the smooth means of the sunspot, 2800-MHz, and plage data. The longitudes of centers of sunspot and flare activity are found to have clustered in identifiable zones or hemispheres for relatively long periods of time. The sun is seen to have had a relatively inactive hemisphere centered about zero deg longitude, and certain well defined coronal holes were apparently located near the middle of this hemisphere. The first sunspot groups of cycle 21 are observed to have formed in the longitude zones associated with relatively high levels of activity during cycle 20.

Dodson, H. W.↗
NASA NTRS1976

The Pioneer 11 1976 solar conjunction: A unique opportunity to explore the heliographic latitudinal variations of the solar corona

The 1976 Pioneer II Solar Conjunction provided the opportunity to accumulate a substantial quantity of doppler noise data over a dynamic range of signal closest approach point heliographic latitudes. The observed doppler noise data were fit to the doppler noise model ISED, and the deviations of the observed doppler noise data from the model were used to construct a (multiplicative) function to describe the effect of heliographic latitude. This expression was then incorporated into the ISED model to produce a new doppler noise model-ISEDB.

Berman, A. L.↗
NASA NTRS1976

Space-based solar power conversion and delivery systems study. Volume 3: Economic analysis of space-based solar power systems

A variety of economic and programmatic issues are discussed concerning the development and deployment of a fleet of space-based solar power satellites (SSPS). The costs, uncertainties and risks associated with the current photovoltaic SSPS configuration, and with issues affecting the development of an economically viable SSPS development program are analyzed. The desirability of a low earth orbit (LEO) demonstration satellite and a geosynchronous (GEO) pilot satellite is examined and critical technology areas are identified. In addition, a preliminary examination of utility interface issues is reported. The main focus of the effort reported is the development of SSPS unit production, and operation and maintenance cost models suitable for incorporation into a risk assessment (Monte Carlo) model (RAM). It is shown that the key technology area deals with the productivity of man in space, not, as might be expected, with some hardware component technology.

Hazelrigg, G. A., Jr.↗
NASA NTRS1977

Solar seismology. II - The stochastic excitation of the solar p-modes by turbulent convection

We test the hypothesis that the solar p-modes are stabilized by damping due to turbulent viscosity in the convective zone. Starting from the assumption that the modes are stable, we calculate expectation values for the modal energies. We find that the interaction between a p-mode and the turbulent convection is such that the modal energy tends toward equipartition with the kinetic energy of turbulent eddies whose lifetimes are comparable to the modal period. From the calculated values of the modal energies, we compute rms surface velocity amplitudes. Our predicted rms surface velocities range from 0.01 cm/sec for the fundamental radial mode to 0.6 cm/sec for the radial mode whose period is approximately 5 minutes. The predicted surface velocities for the low order p-modes are much smaller than the velocities inferred from recent observations.

Goldreich, P.↗
NASA NTRS1977

Possible origins of time variability in Jupiter's outer magnetosphere. I - Variations in solar wind dynamic pressure. II - Variations in solar wind magnetic field

Attention is given to the effect of changes in the dynamic pressure of the solar wind on the structure of a centrifugally driven planetary wind from Jupiter. It is suggested that dynamic pressure variations can induce a transition between a super-Alfvenic wind and a sub-Alfvenic wind breeze on Jupiter's dayside. This could possibly account for the observed large-scale changes in the structure of Jupiter's outer magnetosphere. An attempt is then made to conceptually merge planetary wind models of Jupiter's outer magnetosphere with reconnection models of Jupiter's outer magnetosphere.

Coroniti, F. V.↗
NASA NTRS1977

Momentum and energy transport by waves in the solar atmosphere and solar wind

The fluid equations for the solar wind are presented in a form which includes the momentum and energy flux of waves in a general and consistent way. The concept of conservation of wave action is introduced and is used to derive expressions for the wave energy density as a function of heliocentric distance. The explicit form of the terms due to waves in both the momentum and energy equations are given for radially propagating acoustic, Alfven, and fast mode waves. The effect of waves as a source of momentum is explored by examining the critical points of the momentum equation for isothermal spherically symmetric flow. We find that the principal effect of waves on the solutions is to bring the critical point closer to the sun's surface and to increase the Mach number at the critical point. When a simple model of dissipation is included for acoustic waves, in some cases there are multiple critical points.

Jacques, S. A.↗
NASA NTRS1977

Optimization of solar cells for air mass zero operation and a study of solar cells at high temperatures, phase 3

The etch-back epitaxy process is described for producing thin, graded composition GaAlAs layers. The palladium-aluminum contact system is discussed along with its associated problems. Recent solar cell results under simulated air mass zero light and at elevated temperatures are reported and the growth of thin polycrystalline GaAs films on foreign substrates is developed.

Blakeslee, A. E.↗