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NASA NTRS1979

Hydrogen over helium enhancement in successive solar flare particle events from the same active region

An analysis of all of the identified solar-flare-associated energetic particle events in the 1972-1975 period observed with instruments aboard the IMP 7 and IMP 8 satellites has revealed at least eight occasions when more than one particle-producing flare occurred within the same McMath active plage region during its transit of the visible solar disk. A strong tendency for second flares to produce hydrogen over helium (p/alpha) enhanced energetic particle fluxes when compared with the first flare in the 1.8-10.0 MeV per nucleon range emerged in these multiflare regions. The p/alpha enhancement is apparently transient, and for flares separated by at least about 100 hours the p/alpha ratio tends toward its preflare value. It is suggested that the substrate plasma in an active region may be enriched prior to a flare in elements heavier than hydrogen and the composition may not be significantly altered during subsequent acceleration, escape, and propagation. Thus, the preflare history of the active region must be added to the list of factors influencing observed solar-particle-event composition.

Briggs, P. R.↗

NASA NTRS1978

The importance of spectroscopy in the 80-800 A region for plasma diagnostics in the solar atmosphere

The importance of the spectral range from about 80 to 800 A for determining physical conditions in different regions of the solar atmosphere is discussed. Examples are given of line ratios that may be used to determine electron densities in quiet-sun regions, active regions, and flares. The possibility of determining electron temperatures from line ratios in the EUV is considered. It is shown that profiles, as well as intensities, of spectral lines must be obtained for a proper interpretation of the spectra. Approximate parameters are provided for a solar grazing-incidence spectrograph suitable for the study of the 80-800-A wavelength region.

Feldman, U.↗

NASA NTRS1979

A two-dimensional unsteady Euler-equation solver for flow regions with arbitrary boundaries

A new technique is described for solving supersonic fluid dynamic problems containing multiple regions of continuous flow, each bounded by a permeable or impermeable surface. Region boundaries are, in general, arbitrarily shaped and time dependent. Discretization of such a region for solution by conventional finite difference procedures is accomplished using an elliptic solver which alleviates the dependence on a particular base coordinate system. Multiple regions are coupled together through the boundary conditions. The technique has been applied to a variety of problems including the shock diffraction and pointed wedge with detached bow shock.

Hindman, R. G.↗

NASA NTRS1979

Computing region moments from boundary representations

The class of all possible formulas for computing arbitrary moments of a region from the region's boundary is derived. The selection of a particular formula depends on the choice of an independent parameter. Several choices of this parameter are explored for region boundaries approximated by polygons. The parameter choice that minimizes computation time for boundaries represented by chain code is derived. Algorithms are presented for computing arbitrary moments for a region from a polygonal approximation of its boundary and for computing low order moments from chain encoded boundaries.

Wilf, J. M.↗

NASA NTRS1979

On the continuing stellar formation in the central regions of some globular clusters and their relation to the pulsars

The discrepancy between the predicted and observed quantities of gas in the central regions of massive globular clusters is discussed. It is hypothesized that star formation continues in the central regions by means of gas released during stellar evolution or trapped by the central region when the globular clusters pass through the center of the galaxy. Nine globular clusters are indicated at distances less than 1000 ps from which radio pulsars or X-ray sources are observed. It is argued that they could have formed relatively recently in closed pairs in the central regions and then ejected at the stage of supernova bursts with velocities over 100 ks/s.

Komberg, B. V.↗

NASA NTRS1979

Rocket studies of solar corona and transition region

The XSST (X-Ray Spectrometer/Spectrograph Telescope) rocket payload launched by a Nike Boosted Black Brant was designed to provide high spectral resolution coronal soft X-ray line information on a spectrographic plate, as well as time resolved photo-electric records of pre-selected lines and spectral regions. This spectral data is obtained from a 1 x 10 arc second solar region defined by the paraboloidal telescope of the XSST. The transition region camera provided full disc images in selected spectral intervals originating in lower temperature zones than the emitting regions accessible to the XSST. A H-alpha camera system allowed referencing the measurements to the chromospheric temperatures and altitudes. Payload flight and recovery information is provided along with X-ray photoelectric and UV flight data, transition camera results and a summary of the anomalies encountered. Instrument mechanical stability and spectrometer pointing direction are also examined.

Acton, L. W.↗

NASA NTRS1979

Polar cap electron acceleration regions

The characteristics of polar cap electron acceleration regions and the relationship of their occurrence to the interplanetary magnetic field (IMF) have been investigated by using data from Atmosphere Explorer D and Imp J. It was found that electron energy spectra and angular distributions within the acceleration regions are generally consistent with models of acceleration of auroral primaries and reflection of atmospheric secondaries by field-aligned electrostatic potential differences. However, localized strongly field-aligned fluxes are also observed at energies below the spectral peak. It is suggested that these transient beams of field-aligned low-energy electrons result from the acceleration of thermal electrons from within the acceleration regions and that this thermal electron population may be partially replenished by small pitch angle atmospheric secondaries. The occurrence of the polar cap acceleration regions in the northern hemisphere is strongly correlated with IMF vectors which project into the (-X, +Z) sector of the solar magnetospheric X-Z plane; that is, with northward 'away' IMF polarities.

Burch, J. L.↗

NASA NTRS1979

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

This paper presents the performance and cost of four 10-MWe advanced solar thermal electric power plants sited in various regions of the continental United States. Each region has different insolation characteristics which result in varying collector field areas, plant performance, capital costs, and energy costs. The paraboloidal dish, central receiver, cylindrical parabolic trough, and compound parabolic concentrator (CPC) comprise the advanced concepts studied. This paper contains a discussion of the regional insolation data base, a description of the solar systems' performances and costs, and a presentation of a range for the forecast cost of conventional electricity by region and nationally over the next several decades.

Latta, A. F.↗

NASA NTRS1980

Light ion concentrations and fluxes in the polar regions during magnetically quiet times

Ion concentrations, flow velocities, and fluxes, measured by the ion mass spectrometer on the Isis 2 satellite for periods around the solstices and equinoxes of 1971 and 1972, have been used in a study of the polar wind morphology during magnetically quiet times. The results confirm the major tenets of polar wind theories; namely, that an upward flow of both H(+) and He(+) ions exists at all times over the entire polar region; H(+) fluxes are of the order of 10 to the 8th ions/sq cm s in both summer and winter polar regions. O(+) is the dominant ion specie at 1400-km altitude in regions of strong H(+) flows, and H(+) is depleted over the entire region where the polar wind flows. H(+) fluxes tend to be lower in winter than in summer, whereas He(+) fluxes are a factor of 10 higher in winter and tend to follow the neutral helium concentration near the F2 maximum. The latter agree well with model calculations of flux in the winter but lie above the model values by a factor of 2 in the summer. H(+) fluxes also agree well with ion flow models.

Hoffman, J. H.↗

NASA NTRS1980

CO observations of the galactic star-forming region W58

Observations of (C-12)O and (C-13)O have been made in the direction of the strong galactic radio source W58, which contains the compact H II regions K3-50 and ON-3. An extended molecular cloud with dimensions of 55 x 40 pc is associated with the northern part of the H II region complex. The density of the molecular cloud increases from west to east; the molecular cloud is bounded on the east by a larger H I cloud. Present star-formation activity is taking place at the position of maximum molecular density, at what appears to be the interface of the H I cloud and the H II region complex. The velocity structure of the CO cloud and the compact H II regions are in agreement with the blister model. Radio continuum and H I line observations show indications of a shell structure in the southwest of W58. Present star formation in W58 may be caused by this expanding shell.

Israel, F. P.↗

NASA NTRS1980

Physical properties of individual coronal loops in a solar active region observed in the XUV

The physical properties of individual coronal loops in a solar active region observed in the XUV by the slitless objective grating spectroheliograph on board Skylab are investigated. Spectroheliograms of the normal active loop region McMath 12378 reveal three distinctive structural groups of loops in different temperature ranges, namely (1) small compact and smaller loops at temperatures of about 2,000,000 K observed in Fe XV and Fe XVI; (2) large Ne VII and Mg IX loops at temperatures from 500,000 to 1,000,000 K; and (3) chromospheric ribbons in He II and H alpha. The temperature of the active region is found to be uniform at about 2,000,000 K in the loops and background while loop density is found to be 3.5 x 10 to the 9th/cu cm in the loops and 2.5 x 10 to the 9th/cu cm in the surrounding background. Significant changes in the active region are observed in 24 h, although the gross temperature density structures of many loops do not show changes in 7 min. Gas pressure within the coronal loops is found to be about 40% greater than that of the background plasma. The observed loop parameters are noted to be consistent with flux-limited models of density enhancement in magnetic flux tubes and thus no esoteric heating function is required.

Cheng, C.-C.↗

NASA NTRS1980

Full-coverage film cooling. I - Three-dimensional measurements of turbulence structure. II - Prediction of the recovery-region hydrodynamics

Hydrodynamic measurements of turbulence structure were performed with a triaxial hot wire in the full coverage and the recovery regions following an array of injection holes under isothermal conditions at ambient temperature and pressure for blowing ratios of 0.9 and 0.4. High levels of turbulence kinetic energy (TKE) were determined for low blowing, and low TKE levels were found for the high blowing levels; in the recovery region, the flow can be represented by a model with an outer boundary layer and a 2-dimensional inner boundary layer. Recovery region hydrodynamics can be modelled by considering that a new boundary layer started to grow immediately after the end of blowing; the Prandtl mixing length distributions calculated from the values of mean velocity and turbulent shear stresses were consistent with the presence of a dual boundary layer structure in the recovery region. The program used here contains a one-equation model of turbulence, using turbulence kinetic energy with an algebraic mixing length; this 2-dimensional, finite difference program can predict the mean velocity and turbulence kinetic energy profiles based on initial values, boundary conditions, and a closure condition.

Yavuzkurt, S.↗

NASA NTRS1981

Thermal response of the F region ionosphere in artificial modification experiments by HF radio waves

The thermal response of the nighttime F region ionosphere to local heating by HF radio waves has been observed with the incoherent scatter radar at Arecibo, Puerto Rico. The observations consist of high-resolution space and time variation of the electron temperature as a high-power HF transmitter is switched on and off with a period 240 s. As soon as the HF transmitter is turned on, the electron temperature begins to rise rapidly in a narrow altitude region near 300 km, below the F2 layer peak. The electron temperature perturbation subsequently spreads over a broader altitude region. The observations are compared with the anticipated thermal response of the ionosphere based on numerical solutions of the coupled time-dependent heat conduction equations for the electron and composite ion gases and are found to be in good agreement over the entire altitude region covered by the observations.

Mantas, G. P.↗

NASA NTRS1980

Orientations of central peaks in lunar craters - Implications for regional structural trends

Impact craters are dominant features on the lunar surface and all fresh craters with diameters greater than 35 km possess central peaks. Approximately half of these central peaks (54%) have either linear or arcuate geometry and display some preferential orientation. These orientations were measured for 200 lunar craters of Pre-Nectarian to Copernican age. A pervasive regional north-south trend is identified for central peak orientation, with secondary trends at + or - 20-30 deg from this axis. No evidence for regional east-west trends is found. These orientations are shown to persist in craters formed through the last 4 billion years of lunar history. A lack of coincidence between impact direction, as determined from ejecta asymmetries and peak orientation, argues for structural control by the target as a source of the linear peak morphology. This is supported by the regional and temporal persistence of preferred peak orientations. It is proposed that linear central peak orientations in lunar craters reflect a pervasive regional structural system which developed early in lunar history and has persisted through geologic time.

Hale, W.↗

NASA NTRS1981

X-ray heating and ionization of broad-line emission regions in QSOs and active galaxies

The absorption of X-rays deep within the broad-line emitting clouds in quasars and the nuclei of active galaxies produces extensive zones of warm (about 10,000 K), partially ionized gas. Because Lyman-alpha photons are trapped in these regions, the X-ray energy is efficiently channeled into Balmer lines collisionally excited from the n = 2 level. These H I regions and the H II regions created by UV photons illuminating the surfaces of the clouds gives rise to integrated Lyman-alpha/H-alpha lines emission ratios between 1 and 2. Enhanced Mg II line emission from the H I regions gives rise to integrated Mg II/H-alpha ratios near 0.5. The O I line at 8446 A is efficiently pumped by trapped H-alpha photons; and an intensity ratio of I(8446 A)/I(H-alpha) of approximately equal to and not greater than 0.1 is calculated for the X-ray heated zone.

Weisheit, J. C.↗

NASA NTRS1982

Fresnel-region fields and antenna noise-temperature calculations for advanced microwave sounding units

A transition from the antenna noise temperature formulation for extended noise sources in the far-field or Fraunhofer-region of an antenna to one of the intermediate near field or Fresnel-region is discussed. The effort is directed toward microwave antenna simulations and high-speed digital computer analysis of radiometric sounding units used to obtain water vapor and temperature profiles of the atmosphere. Fresnel-region fields are compared at various distances from the aperture. The antenna noise temperature contribution of an annular noise source is computed in the Fresnel-region (D squared/16 lambda) for a 13.2 cm diameter offset-paraboloid aperture at 60 GHz. The time-average Poynting vector is used to effect the computation.

Schmidt, R. F.↗

NASA NTRS1982

Regional applicability and potential of salt-gradient solar ponds in the United States. Volume 2: Detailed report

A comprehensive assessment of the regional applicability and potential of salt-gradient solar ponds in the United States is provided. The assessment is focused on the general characteristics of twelve defined geographic regions. Natural resources essential to solar ponds are surveyed. Meteorological and hydrogeological conditions affecting pond performance are examined. Potentially favorable pond sites are identified. Regional thermal and electrical energy output from solar ponds is calculated. Selected pond design cases are studied. Five major potential market sectors are evaluated in terms of technical and energy-consumption characteristics, and solar-pond applicability and potential. Relevant pond system data and financial factors are analyzed. Solar-pond energy costs are compared with conventional energy costs. The assessment concludes that, excepting Alaska, ponds are applicable in all regions for at least two market sectors. Total solar pond energy supply potential in the five market sectors examined is estimated to be 8.94 quads/yr by the year 2000, approximately 7.2% of the projected total national energy demand.

Lin, E. I. H.↗

NASA NTRS1981

Ion and electron angular distributions in the Io torus region of the Jovian magnetosphere

Angular distributions are presented of ion (about 0.5-2 MeV) and electron (greater than 10 MeV) fluxes measured during the Voyager 1 spacecraft passage through the inner regions of the Jovian magnetosphere. In the regions of peak flux intensities, just outside the orbit of Io, the ion angular distributions are most sharply peaked at 90 deg local pitch angle, a configuration consistent with diffusion of the particles inward from large radial distances. Inside the orbit of Io the lower-energy ions exhibit angular distributions depleted at 90 deg local pitch angles, suggesting the possibility of charge-exchange scattering loss of these particles. In the vicinity of the Io flux tube, no significant effect is observed in the flux or pitch angle distributions of the ions. The relativistic electrons are depleted in the flux tube region and exhibit an asymmetrical pitch angle distribution, with more electrons appearing to arrive from the equatorial region (the direction of Io) than from the low-altitude mirror point.

Lanzerotti, L. J.↗