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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Solar cycle changes in the high latitude solar wind

Measurements of the solar wind velocity during the period 1971-79 using the technique of interplanetary scintillation are discussed. The average wind speed was faster than 500 km/s at latitudes above 30 deg for most of 1973-77. The fast polar stream, observed to become much narrower in 1978-79 is examined. The narrowing of the polar streams coincided with the emergence of sunspots at midlatitudes, with the start of the new solar cycle, and with a corresponding contraction of the polar coronal holes. The theory that the solar magnetic field controls the large scale structure of the solar wind is discussed in relation to the results.

Rickett, B. J.↗
NASA NTRS1979

Solar Activities Predictions: Long-Term Solar Activity

The need for long term solar activity predictions is addressed. The spatial organization of solar activity is described including applications for predictions, and ancient evidence for solar variability. Methods of predicting sunspot numbers are discussed. The inherent accuracy of the methods varies considerably, but a typical error bar 20%. The accuracy of sunspot cycle predictions is considered along with long term predictions of great solar events.

P S Mcintosh↗
NASA NTRS1980

Solar heating and hot water system installed at office building, One Solar Place, Dallas, Texas

A solar heating on cooling system is described which is designed to provide 87 percent of the space heating needs, 100 percent of the potable hot water needs and is sized for future absorption cooling. The collection subsystem consists of 28 solargenics, series 76, flat plate collectors with a total area of 1,596 square feet. The solar loop circulates an ethylene glyco water solution through the collectors into a hot water system exchanger. The water storage subsystem consists of a heat exchanger, two 2,300 gallon concrete hot water storage tanks with built in heat exchangers and a back-up electric boiler. The domestic hot water subsystem sends hot water to the 10,200 square feet floor area office building hot water water fixtures. The building cold water system provides make up to the solar loop, the heating loop, and the hot water concrete storage tanks. The design, construction, cost analysis, operation and maintenance of the solar system are described.

Source record↗
NASA NTRS1980

Variations in the solar constant due to solar active regions

Solar activity is expected to affect the solar constant at some level. Recent observations and data analysis show the amount of variation to be expected for active regions, faculae, and sunspots on the apparent solar brightness. It is concluded that the maximum effect is about 20 times greater for sunspots than for faculae per unit area. Because facular areas are 25-30 times those for sunspots, the effect on the solar constant of faculae and sunspots is approximately equal and opposite, being typically in the neighborhood of 40-100 parts per million (ppm), but on occasion able to reach over 200 ppm. The issue of energy balance is not discussed here, for it requires further data analysis as well as information on the facular and sunspot limb darkening.

Chapman, G. A.↗
NASA NTRS1981

Solar flare acceleration of solar wind - Influence of active region magnetic field

The direction of the photospheric magnetic field at the site of a solar flare is a good predictor of whether the flare will accelerate solar wind plasma. If the field has a southward component, high-speed solar wind plasma is usually observed near the earth about 4 days later. If the field has a northward component, such high-speed solar wind is almost never observed. Southward-field flares may then be expected to have much larger terrestrial effects than northward flares.

Lundstedt, H.↗
NASA NTRS1980

Determination of variations of the solar radius from solar eclipse observations

This paper describes the method to determine the solar radius and its variations from observations made during total solar eclipses. In particular, the procedure to correct the spherical moon predictions for the effects of lunar mountains and valleys on the width and location of the path of totality is addressed in detail. The errors affecting this technique are addressed, a summary of the results of its application to three solar eclipses are presented, and the implications of the results on the constancy of the solar constant are described.

Sofia, S.↗
NASA NTRS1982

Optical characterization of solar concentrator mirrors using the solar beam of the JPL 25-foot space simulator

The Jet Propulsion Laboratory 25-foot space simulator with its 5.8-m (19-ft) diameter simulated solar beam provides an excellent facility for measuring the optical characteristics of parabolic solar concentrator panels and gores. The virtual source position and size were determined by using a single lamp of the 37 xenon 30-kW source array with only the center lens in the 19-channel optical mixer. This data was used to define the optical test geometry, and it allowed accurate measurement of focal length and surface deviations of the mirror under test. A flux distribution of a typical solar concentrator placed directly on the solar beam gives measurements of performance at the focal point of the parabolic surface.

Argoud, M. J.↗
NASA NTRS1981

The solar spectral irradiance 1200-3184 A near solar maximum - July 15, 1980

Results of a sounding rocket program designed to measure the total solar ultraviolet input to the upper atmosphere are presented. Two spectrometers, a far-ultraviolet (FUV) to cover 1160-1850 A, and a middle ultraviolet (MUV) to cover 1600-3184 A, were launched piggy-back on a Black Brant rocket to an altitude of 325 km on 7-15-1980. Tables of the detailed error budgets of the reclaimed instruments are provided. Comparisons are made with results of a 1979 flight, and of 1979 and 1980 flights with solar minimum results of Rottman (1981), and reveal significant solar spectral irradiance variability from solar minimum to maximum. MUV readings below 2100 A were 14% higher in 1980 and 14% lower in 1979 than Rottman's data, and it is concluded that a significant variability occurred at wavelengths less than 1800 A.

Mount, G. H.↗
NASA NTRS1982

The influence of solar active region evolution on solar wind streams, coronal hole boundaries and geomagnetic storms

Solar and interplanetary data are examined, taking into account the identification of the heliographic longitudes of the coronal source regions of high speed solar wind (SW) streams by Nolte and Roelof (1973). Nolte and Roelof have 'mapped' the velocities measured near earth back to the sun using the approximation of constant radial velocity. The 'Carrington carpet' for rotations 1597-1616 is shown in a graph. Coronal sources of high speed streams appear in the form of solid black areas. The contours of the stream sources are laid on 'evolutionary charts' of solar active region histories for the Southern and Northern Hemispheres. Questions regarding the interplay of active regions and solar wind are investigated, giving attention to developments during the years 1973, 1974, and 1975.

Gold, R. E.↗
NASA NTRS1981

Study of the response of stratospheric ozone to perturbations in the solar constant and solar UV flux

A one-dimensional radiative-convective photochemical model has been used to examine the response of stratospheric and total ozone to perturbations in the solar flux. The model considers a detailed chemical reaction mechanism; vertical transport is parameterized through eddy diffusion coefficients. The temperature profile is calculated using a radiative transfer model for both time-dependent and steady-state cases. Results are discussed for the following types of perturbations: a 5% increase in the solar UV flux in the wavelength range 175-300 nm, a 5% increase in the solar constant, and an annual 6.6% variation in the solar constant associated with the variation in the earth-sun distance.

Natarajan, M.↗
NASA NTRS1982

Solar wind iron abundance variations at solar wind speeds up to 600 km s sup -1, 1972 to 1976

The Fe/H ratios in the peaks of high speed streams (HSS) were analyzed during the decline of Solar Cycle 20 and the following minimum (October 1972 to December 1976). The response of the 50 to 200 keV ion channel of the APL/JHU energetic particle experiment (EPE) on IMP-7 and 8 was utilized to solar wind iron ions at high solar wind speeds (V or = 600 km/sec). Fe measurements with solar wind H and He parameters were compared from the Los Alamos National Laboratory (LANL) instruments on the same spacecraft. In general, the Fe distribution parameters (bulk velocity, flow direction, temperature) are found to be similar to the LANL He parameters. Although the average Fe/H ration in many steady HSS peaks agrees within observational uncertainties with the nominal coronal ratio of 4.7 x 0.00001, abundance variations of a factor of up to 6 are obtained across a given coronal-hole associated HSS.

Mitchell, D. G.↗
NASA NTRS1983

Solar wind flow about the terrestrial planets. II - Comparison with gas dynamic theory and implications for solar-planetary interactions

Bow shock models are employed to determine and compare the solar wind flows about Venus, Mars, and the earth. Initially, gas dynamic theory predictions are compared with the large data base available for the near-earth environment. The observed shape and location of the magnetopause proved sufficient for predicting the average dayside bow shock position to within 2% error. Use of the same gas dynamics theory produced highly disparate results for the flows past Venus and Mars. A variation of 510-1000 km altitude (high) for the solar wind-obstacle interface was found for Mars, thus requiring the presence of an effective magnetic moment of within 0.6 of 1.4 x 10 to the 22nd G/cu cm in the Martian magnetosphere, consistent with Viking data. The Venus bow wave was calculated to be closer to the planet than possible with a purely ionospheric interaction, indicating that solar wind-neutral atmosphere interactions in the lower ionosheath must necessarily be included in a gas dynamic modeling of the Venus obstacle to the solar wind.

Slavin, J. A.↗
NASA NTRS1983

Testing solar models with global solar oscillations in the 5-minute band

Frequencies of solar oscillation for normal modes described by spherical harmonics with l-values between 0 and 4 are computed. The method of computation is discussed and some of the theoretical uncertainties are examined. It is shown that the standard solar model has eigenfrequencies which do not agree with the frequencies observed for the low l-modes to within the estimated accuracy of either the observed or theoretical frequencies. Four non-standard models are considered: (1) the interior Z abundance is lower than the surface abundance; (2) the interior Z abundance is higher than the surface abundance; (3) the interior Z abundance is altered by mixing; and (4) a large primordial magnetic field remains in the solar core. The effect of all these models on the solar neutrino flux is considered, with the result that the high-Z model is rejected. The conclusions of Bahcall and Ulrich (1971) that a primordial magnetic field increases the neutrino flux are disputed.

Ulrich, R. K.↗
NASA NTRS1984

Temporal Variations of Solar UV Spectral Irradiance Caused by Solar Rotation and Active Region Evolution

Variations in the solar 100 to 400 nm UV spectral irradiance caused by solar rotation and active region evolution, are discussed as a function of UV wavelength, CMD dependence, and in relation to the temporal variations in the total solar irradiance, 10.7 cm radio flux, sunspot number and Ca K plage data. Active region radiation at cm wavelengths includes a component proportional to the magnetic field. Active region evolution involves a more rapid growth, peak and decay of sunspots and their strong magnetic fields than the Ca K plages and their related UV enhancements. Major plages often last a rotation or more longer than the active region's sunspots. Large active regions, including those associated with major dips in the total solar irradiance, tend to produce the strongest peaks in 10.7 cm and sunspot numbers on their first rotation, while the Ca K plages and UV enhancements peak on the next rotation and decay more slowly on subsequent rotations. Differences in CMD dependencies cause temporal differences including the stronger presence of 13 day variations in the UV flux.

Donnelly, R. F.↗
NASA NTRS1983

Solar wind disturbances caused by solar flares - Equatorial plane

The propagation of solar wind disturbances caused by single, double and six successive flares in the dipolar and quadrupolar patterns of the interplanetary magnetic field (IMF) and the associated solar wind flow is studied. This study is based on a kinematic and empirical method developed by Hakamada and Akasofu (1982). Each flare is characterized by six parameters (such as the highest speed flow, its extent and duration). The successive IMF patterns in the equatorial plane of the heliosphere during a time span of 0.5-60 days after flares are presented for a variety of flares. The solar wind speed and IMF magnitude are given as a function of distance along a radial line fixed in space and also as a function of time at several points fixed in space (simulating approximately space probe observations). Some of the results are qualitatively compared with recent space probe observations, demonstrating fair similarity with the observed time profiles of solar wind speed variations over a wide range of both distances (0-10 AU) and time spans (60 days). The method provides a first-order construction, temporal and spatial, of flare-induced shocks and their multiple interactions with each other, as well as with the corotating interaction regions.

Akasofu, S.-I.↗
NASA NTRS1983

Exospheric cleaning of the Earth Radiation Budget solar radiometer during solar maximum

Anomalous behavior of the Earth Sensor Assemblies (ESA) had been observed on the Defense Meteorological Satellite Program (DMSP) 5D/1 satellites and the Tiros-N satellite. The present investigation is concerned with the reasons for the observed phenomena. Degradation of the Earth Radiation Budget (ERB) solar channels and the Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer (SBUV/TOMS) diffuser plate is attributed to transmission or reflection loss originating from the growth of an organic film by photolytic polymerization. Simultaneous degradation of the ESA interference filter coated lenses facing the flight direction and the recovery of the ERB solar channels on Nimbus 6 and 7 is caused by a reaction with the increase in the exospheric atmospheric density caused by solar maximum.

Predmore, R. E.↗
NASA NTRS1985

The 4He1H ratios in the chemical compositions of solar flare particles and the primordial solar nebula

The chemical abundances of solar flare particles are similar to those of galactic cosmic rays at their sources. In order to infer the 4He/1H ratio in the solar atmosphere, this ratio as observed in the interstellar gases was considered in addition to those which were contained of galactic cosmic rays and the stars classified as the early types. Since it is clear that the most of these ratios ever deduced for both of the Sun and solar flare particles are lower than those for the interstellar gases, this ratio suggests that hydrogens are relatively overabundant in the chemical abundances of the Sun and the primordial solar nebula as compared to those of the interstellar gases currently observed.

Sakurai, K.↗