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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Structure of the chromosphere-corona transition region.

The structure and energy balance of the chromosphere-corona transition region is investigated by means of a static, planar model which is compared with the results of XUV-resonance-line observations. In this model, the transition region is heated by thermal conduction from the corona and cooled by radiative losses. Comparison of the model with observational results implies that this is the dominant process in the energy balance of the transition region, and that the base of the transition region is inherently nonstatic and/or nonplanar. The model explains the observational finding of Noyes et al. (1970) that the number density and the downward heat flux both increase by the same factor from quiet regions to active regions.

Moore, R. L.↗
NASA NTRS1973

Molecular flux measurements in the back flow region of a nozzle plume

A series of tests were conducted to measure the mass flux in the far field of a nozzle plume in a high vacuum with emphasis on the back flow region. The measurements presented provided fairly accurate data for off-axis angles as large as 140 deg (i.e., in the back flow region). This region, since it is well behind the exit plane, is of paticular interest to those concerned with instrument contamination. Usually sensitive spacecraft surfaces are located in the region affected by the back flow. Parameters such as expansion ratio, throat diameter, nozzle lip shape, and plenum (chamber) pressure were varied, carbon dioxide and nitrogen gases were flowed and mass flux measurements were taken using quartz crystal microbalances in as many as nine different locations relative to the tests nozzle. Several conclusions with respect to the effect of nozzle and gas parameters on the amount of back flow mass flux are offered, and it was demonstrated that gaseous mass fluxes, which are not predictable by present theories, are encountered in the region behind the nozzle exit plane. This knowledge is significant if materials incompatible with the gaseous exhaust products are used in this region.

Chirivella, J. E.↗
NASA NTRS1976

Skylab observations of X-ray loops connecting separate active regions

One hundred loops interconnecting 94 separate active solar regions detectable in soft X-rays were identified during the Skylab mission. While close active regions are commonly interconnected with loops, the number of such interconnections decreases steeply for longer distances; the longest interconnecting loop observed in the Skylab data connected regions separated by 37 deg. Several arguments are presented which support the point of view that this is the actual limit of the size of magnetic interconnections between active regions. No sympathetic flares could be found in the interconnected regions. These results cast doubt on the hypothesis that accelerated particles can be guided in interconnecting loops from one active region to another over distances of 100 deg or more and eventually produce sympathetic flares in them.

Chase, R. C.↗
NASA NTRS1977

6 centimeter observations of solar active regions with 6 sec resolution

We have used the Westerbork Synthesis Radio Telescope for observations of solar active regions at 6 cm during 1974 May 8-10. The particular problems of using a sidereal instrument for solar observations are discussed. Maps of total intensity and circular polarization were obtained for four active regions with sunspots and a plage region; the linear polarization was below the noise limit. The brightest components of the 6 cm emission are associated with sunspots, while weaker components are associated with the plage magnetic fields, both longitudinal and transverse. An inversion of the sense of circular polarization was observed in the preceding part of a region with bipolar magnetic-field structure, about two days after the region passed through the central meridian. Nine bursts were also observed, and their one-dimensional positions with respect to the associated active regions are given.

Kundu, M. R.↗
NASA NTRS1977

Open magnetic fields in active regions

Soft X-ray images and magnetograms of several active regions and coronal holes are examined which support the interpretation that some of the dark X-ray gaps seen between interconnecting loops and inner cores of active regions are foot points of open field lines inside the active regions. Characteristics of the investigated dark gaps are summarized. All the active regions with dark X-ray gaps at the proper place and with the correct polarity predicted by global potential extrapolation of photospheric magnetic fields are shown to be old active regions, indicating that field opening is accomplished only in a late phase of active-region development. It is noted that some of the observed dark gaps probably have nothing in common with open fields, but are either due to the decreased temperature in low-lying portions of interconnecting loops or are the roots of higher and less dense or cooler loops.

Svestka, Z.↗
NASA NTRS1978

E region coupling effects on the Perkins spread F instability

The Perkins instability theory for mid-latitude spread F is generalized to include the effects of the E region on growth rates. A three-layer model, representing the E region, the F region, and a resistive layer of low Pedersen conductivity which separates them, is developed. The E region Pedersen current has a stabilizing effect on the perturbed F region, thereby reducing the growth rate of the instability. For spread F onset on September 17, 1974, the maximum growth rate is found to be only one third of the Perkins growth rate. The resistive layer reduces the electric field perturbation in the E region for short wavelengths but has little effect for long wavelengths.

Klevans, E. H.↗
NASA NTRS1979

Far-infrared observations of the Carina I and II H II regions

Far-infrared (35-175 microns) mapping and photometry are presented of the Carina I and II H II regions in the Carina Nebula (NGC 3372). The far-infrared source associated with Carina I has a half-power width of 2.7 arcmin and has no compact high-surface-brightness condensations, unlike many northern H II regions such as W51 or W49. The peak emission region is offset from the radio continuum peak in the direction of a dust lane to the west. It is proposed that the H II regions and far-IR source are both powered by the O-star cluster Tr 14 about 4 arcmin to the east. The H II region then represents an ionization front at the boundary of the dense cloud west of Tr 14, and the far-infrared emission is due to thermal radiation from the heated dust in the dark cloud. A similar model may also be applicable to the Carina II region.

Harvey, P. M.↗
NASA NTRS1979

Modeling of radiative heating of base region of Jovian entry probe

The mechanism of radiative heating of the afterbody region of Jovian entry probe is analyzed. A theoretical model is derived to determine the average thermodynamic properties in the expanding region, recirculating region, recompression region, and neck region through application of one-dimensional conservation equations. Flow parameters are obtained from the shadowgraphs of a free-flight test. Radiative transfer is calculated using spectrally detailed computer codes accounting for nonequilibrium. The results show that the most severe heating occurs immediately behind the frustum, and that the recompression and neck regions are the major sources of radiation that heats the base stagnation point. The radiation flux to the base point is slightly stronger with ablation than without, its value being 0.11(43Pb/Ps)squared times that to the front stagnation point, where Pb/Ps is the ratio of base-to-front stagnation point pressures and its value is in the range 0.023-0.066. The time-integrated heat load to the base point is 18(43Pb/Ps)squared kJ/sq cm. Existing experimental data are shown to agree with the theoretical prediction.

Park, C.↗
NASA NTRS1980

Glucose metabolism in different regions of the rat brain under hypokinetic stress influence

Glucose metabolism in rats kept under long term hypokinetic stress was studied in 7 brain regions. Determination was made of the regional levels of glucose, lactate, glutamate, glutamine, aspartate, gamma-aminobutyrate and the incorporation of C-14 from plasma glucose into these metabolites, in glycogen and protein. From the content and activity data the regional glucose flux was approximated quantitatively. Under normal conditions the activity gradient cortex and frontal pole cerebellum, thalamus and mesencephalon, hypothalamus and pons and medulla is identical with that of the regional blood supply (measured with I131 serum albumin as the blood marker). Within the first days of immobilization a functional hypoxia occurred in all brain regions and the utilization of cycle amino acids for protein synthesis was strongly diminished. After the first week of stress the capillary volumes of all regions increased, aerobic glucose metabolism was enhanced (factors 1.3 - 2.0) and the incorporation of glucose C-14 via cycle amino acids into protein was considerably potentiated. The metabolic parameters normalized between the 7th and 11th week of stress. Blood supply and metabolic rate increased most in the hypothalamus.

Konitzer, K.↗
NASA NTRS1980

The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs

The performance and cost of four 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States was studied. Each region has different insolation characteristics which result in varying collector field areas, plant performance, capital costs and energy costs. The regional variation in solar plant performance was assessed in relation to the expected rise in the future cost of residential and commercial electricity supplied by conventional utility power systems in the same regions. A discussion of the regional insolation data base is presented along with a description of the solar systems performance and costs. A range for the forecast cost of conventional electricity by region and nationally over the next several decades is given.

Latta, A. F.↗
NASA NTRS1980

CO observations of several galactic H II regions

Maps of the CO emission at a resolution of 8 arcmin are presented for seven H II regions or H II region groups; the results of a search for CO emission near seven more are also given. CO was detected near all but two of the observed objects. The distribution of (C-12)O and (C-13)O near S142, S157, and S159 was mapped at a resolution of 2.3 arcmin. The S147/S153 group of H II regions is shown to consist of physically related objects; it is a region of active star formation. The results show a complicated molecular cloud structure near most observed H II regions. There is a tendency for decreasing CO cloud mass when H II regions in more evolved stages are observed. The relevance of these results for the understanding of individual H II region/molecular cloud complexes, and for general aspects of the star-formation process, is briefly discussed.

Israel, F. P.↗
NASA NTRS1982

The NGC 7538 region - The distribution and dynamics of molecules compared with those of HI and H/+/

CO maps and preliminary H2S and H2CO data for the molecular cloud associated with the HII region NGC 7538 are compared with the distributions of ionized and neutral hydrogen. South of the optical HII region is a ridge of high (C-13)O column density with cold, self-absorbed HI gas just beyond it. A dense clump within thy ridge is found adjacent to the HII region in the southeast. The percentage of the hydrogen in atomic form varies from approximately 0.1% in the dense region to approximately 0.8% in the outskirts. The lower-density region of expanding gas seen next to the HII region in the southwest is attributed to the passage of a molecular dissociation wave.

Dickel, H. R.↗
NASA NTRS1983

Crosscutting relations and relative ages of ridges and faults in the Tharsis region of Mars

The results of a detailed photogeologic analysis and classification of ridge-fault cross-cutting relationships on ridged plains units of the Tharsis region is reported. The problems involved in using the morphology of ridge-fault intersections to determine relative timing of structural events are discussed. The implications of using intersection angles as well as morphology to determine possible age relationships for the tectonic history of the region are presented. It is concluded that the major ridge-forming events in the Tharsis region were roughly coincident with, and possibly prior to, the extensional events that produced the faulting of the Tempe and Mareotis regions, the Coprates and Memnonia regions, and the rifting of the Valles Marineris. The compressional events that formed most of the ridges are restricted in time both by their relationship to regional extensional events and by the age of the units on which they formed.

Watters, T. R.↗
NASA NTRS1983

Nonthermal components of low energy electrons in the ionospheric E and F region

Rocket-borne instrument observations of very low energy electrons' energy distribution in the ionospheric E and F regions showed the regions to exist where an enhanced, high energy tail of thermal electrons appeared. One such appearance was amid a region of high electron temperature, T(e),associated with the Sq anomaly, where there were large T(e) deviations from the neutral temperature. The associated electron heating was most intense at 107 km, gradually decreasing toward 130 km, where both the T(e) and the excess high energy tail became small. In the second region, excess electrons appeared in the high energy tail at 135 km, reached an intensity peak at 150 km, and gradually decreased toward 210 km. It is suggested that the anomalously elevated T(e) and the enhanced energy tail in the first region were locally generated by some dynamo current-related mechanism distinct from Joule heating. The second region's high energy tail is also related to ionospheric currents.

Oyama, K. I.↗
NASA NTRS1984

Depth of origin of solar active regions

Observations show that the individual bipolar magnetic regions on the sun remain confined during their decay phase, with much of the magnetic field pulling back under the surface, in reverse of the earlier emergence. This suggests that the magnetic field is held on a short rein by subsurface forces, for otherwise the region would decay entirely by dispersing across the face of the sun. With the simple assumption that the fields at the surface are controlled from well-defined anchor points at a depth h, it is possible to relate the length l of the bipolar region at the surface to the depth h, with h about equal to l. The observed dimensions l about equal to 100,000 km for normal active regions, and l about equal to 10,000 km for the ephemeral active regions, indicate comparable depths of origin. More detailed observational studies of the active regions may be expected to shed further light on the problem.

Parker, E. N.↗
NASA NTRS1985

Accurate Albedos of the Brightest Regions on Io

The brightest, coldest areas on Io, the white regions, may act as cold traps for SO2 gas, and thus have an important role in governing the pressure, diurnal variation, and flow of the satellite's tenuous SO2 atmosphere. Therefore, it is essential to derive accurate albedos for the brightest regions, where the necessary albedos are those in the energy balance equation of the surface used to compute temperatures. Forty-one of the brightest of the white areas, each 60 to 120 km on a side were studied. The simplest way to estimate the required energy balance albedo for each region is to determine the Bond slbedo of a planet covered with that type of material. This process is outlined and resulting albedos are given. with the exception of several darker regions on the poorly-resolved post eclipse face of Io, typical albedos are 0.6 to 0.7. The brightest areas studied are located in the cluster of white regions east of Prometheus (longitudes 90 to 40 deg W). It is possible using Voyager data and fits to Hapke's equation to derive albedos for the bright regions without making any assumptions about the phase integrals.

Simonelli, D. P.↗
NASA NTRS1984

Homologous flares and the evolution of NOAA Active Region 2372

A detailed record of the evolution of NOAA Active Region 2372 has been compiled by the FBS Homology Study Group. It was one of the most prolific flare-producing regions observed by SMM. The flares occurred in distinct stages which corresponded to particular evolutionary phases in the development of the active region magnetic field. By comparison with a similar but less productive active region, it is found that the activity seems to be related to the magnetic complexity of the region and the amount of shear in the field. Further, the soft X-ray emission in the quiescent active region is related to its flare rate. Within the broader definition of homology adopted, there was a degree of homology between the events within each stage of evolution of AR2372.

Strong, K. T.↗
NASA NTRS1984

Relationships of a growing magnetic flux region to flares

The evolution of flare sites at the boundaries of major new and growing magnetic flux regions within complexes of active regions has been analyzed using H-alpha images. A spectrum of possible relationships of growing flux regions to flares is described. An 'intimate' interaction between old and new flux and flare sites occurs at the boundaries of their regions. Forced or 'intimidated' interaction involves new flux pushing older, lower flux density fields toward a neighboring old polarity inversion line, followed by the occurrence of a flare. In 'influential' interaction, magnetic lines of force over an old polarity inversion line reconnect to new emerging flux, and a flare occurs when the magnetic field overlying the filament becomes too weak to prevent its eruption. 'Inconsequential' interaction occurs when a new flux region is too small or has the wrong orientation for creating flare conditions. 'Incidental' interaction involves a flare occurring without any significant relationship to new flux regions.

Martin, S. F.↗