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NASA NTRS1982

Active region magnetic fields inferred from simultaneous VLA microwave maps, X-ray spectroheliograms, and magnetograms

The VLA maps at 6-cm wavelength discussed here are generated from observations of a solar active region (NOAA 2363) on March 29 and 30, 1980. The X-ray spectroheliograms were acquired for this region in the lines of O VIII, Ne IX, Mg XI, Si XIII, S XV, and Fe XXV. It is found that the peaks of X-ray and 6-cm emission do not coincide but that the sources in the two wavelength domains tend to overlap. These facts are seen as evidence for the existence of opacity mechanisms other than thermal bremsstrahlung. To quantify this assertion, differential emission measures are computed to derive densities and temperatures. Using these and calculated force-free magnetic fields from Kitt Peak magnetograms, an assessment is made of the mechanism of gyroresonance absorption at low harmonics of the electron gyrofrequency as the source of opacity responsible for the microwave features. It is concluded that large-scale currents must be present in the active region loops to account for the bright 6-cm sources far from sunspots.

Schmahl, E. J.↗

NASA NTRS1982

Transmission of CO2 in the atmosphere of Venus for the spectral region near 7 microns

The transmission in the 7-micron 'window' of Venus was calculated for a 7-layer model atmosphere. The synthetic spectra show that radiation from the layer 20-30 km above the surface would reach the top of the atmosphere between 6.2 and 7.0 microns if there were no absorption besides the isotopic CO2 bands; for the 7.0- to 8.2-micron region, the radiating level would be located 40-50 km above the surface of Venus. The brightness temperature for the entire region is 430 K; for the above two regions it is 494 and 341 K, respectively.

Young, L. G.↗

NASA NTRS1982

Regional thermal and electric energy output of salt-gradient solar ponds in the U.S.

Salt-gradient solar pond thermal and electrical energy output was calculated for each of twelve regions within the United States as part of an effort to assess solar pond applicability and extent of requisite physical resources on a regional basis. The energy output level is one of the key factors affecting the economic feasibility of solar ponds. Calculated thermal energy output ranges from 6.9 Wt/sq m in Fairbanks, Alaska, to 73.1 Wt/sq m in Daggett, California, at an energy extraction temperature of 45 C. The output ranges from 0.0 Wt/sq m in Fairbanks to 63.2 Wt/sq m in Daggett at 60 C. Electrical energy output ranges from 0.0 We/sq m in Fairbanks to 3.11 We/sq m in Daggett. Although these estimates constitute a reasonable basis for regional comparison, site-specific analysis must be performed for an actual application design.

Singer, M. J.↗

NASA NTRS1983

Influence of the E region dynamo on equatorial spread F

The integrated E region Pedersen conductivity can be an important parameter in determining whether the bottomside of the equatorial F layer will be stable against the Rayleigh-Taylor gravitational instability. The F layer is observed to become unstable when it rises to great heights after sunset. One effect of this height rise is to decrease the stabilizing influence of ion-neutral collisions at F region heights. It is shown here that the same eastward electric field that raises the F layer also decreases the Pedersen conductivity of the E region, which further destabilizes convective overturning. Because the conductivity of magnetic tubes that penetrate the main F layer is large compared to the E layer contribution, these effects are important only for the bottomside of the equatorial F layer.

Hanson, W. B.↗

NASA NTRS1983

Turbulent heat transfer in the separated reattached and redevelopment regions of a circular tube

A numerical study is reported on a flow in a circular pipe with an abrupt expansion. In this paper the behavior of flow in the domain including recirculating and redeveloping regions has been reviewed carefully and a new grid system is employed which provides finer grids in the recirculating region and monotonically expanding grids in the redeveloping region. The predicted results were improved for the class of this flow by incorporating and adapting the low-Reynolds number model of turbulence throughout the solution domain. The computational results obtained by the present model generally are better than the former results of the authors, particularly in the prediction of the reattachment points.

Amano, R. S.↗

NASA NTRS1983

Voyager 2 observations of energetic particle variations in the Ganymede wake region - A possible acceleration mechanism

Voyager 2's passage through the downstream corotation region of Ganymede found disturbances in the field and particle environment. Large fluctuations in the intensities and energy spectra of ions in the 0.1-to 4.0-MeV interval were also observed with the low energy charged particle experiment. All ion species were evidently affected, up through medium (C, N, O) nuclei. Electrons intensities, while disturbed, did not behave similarly to the ions. These effects are probably associated with the wake produced by the absorption of Jovian magnetospheric corotating plasma by Ganymede. A two-dimensional theoretical model for perturbed field in the wake region is proposed and it is shown by direct numerical simulation of exact particle trajectories that such perturbations are capable of modulating the charged particle energies to about the observed amount for the observed magnetic and plasma parameters. Analysis shows that the energization process is dependent on the pitch angles of the energetic ions and the process itself is nonadiabatic (the Larmor radius is approximately the size of the disturbance region).

Tariq, G.F.↗

NASA NTRS1983

Energetic ion acceleration and transport in the upstream region of Jupiter - Voyager 1 and 2

Long-lived upstream energetic ion events at Jupiter appear to be very similar in nearly all respects to upstream ion events at earth. A notable difference between the two planetary systems is the enhanced heavy ion compositional signature reported for the Jovian events. This compositional feature has suggested that ions escaping from the Jovian magnetosphere play an important role in forming upstream ion populations at Jupiter. In contrast, models of energetic upstream ions at earth emphasize in situ acceleration of reflected solar wind ions within the upstream region itself. Using Voyager 1 and 2 energetic ion measurements near the magnetopause, in the magnetosheath, and immediately upstream of the bow shock, the compositional patterns are examined together with typical energy spectra in each of these regions. Characteristic spectral changes are found late in ion events observed upstream of the bow shock at the same time that heavy ion fluxes are enhanced and energetic electrons are present. A model involving upstream Fermi acceleration early in events and emphasizing energetic particle escape in the prenoon part of the Jovian magnetospehre late in events is presented to explain many of the features in the upstream region of Jupiter.

Baker, D. N.↗

NASA NTRS1983

A conservative type-dependent full potential method for the treatment of supersonic flows with embedded subsonic regions

A nonlinear method based on the full potential equation in conservation form, cast in an arbitrary coordinate system, has been developed to treat predominantly supersonic flows with embedded subsonic regions. This type of flow field occurs frequently near the fuselage-canopy junction area and wing leading edge regions for a moderately swept fighter configuration. The method uses the theory of characteristics to accurately monitor the type-dependent flow field. A conservative switching scheme is developed to transition from the supersonic marching algorithm to a subsonic relaxation procedure, and vice versa. An implicit approximate factorization scheme is employed to solve the finite-differenced equation. Results are shown for a few configurations, including a wing-body-wake realistic fighter model having embedded subsonic regions.

Shankar, V.↗

NASA NTRS1983

High resolution telescope and spectrograph observations of solar fine structure in the 1600 A region

High spatial resolution spectroheliograms of the 1600 A region obtained during the HRTS rocket flight of 1978 February 13 are presented. The morphology, fine structure, and temporal behavior of emission bright points (BPs) in active and quiet regions are illustrated. In quiet regions, network elements persist as morphological units, although individual BPs may vary in intensity while usually lasting the flight duration. In cell centers, the BPs are highly variable on a 1 minute time scale. BPs in plages remain more constant in brightness over the observing sequence. BPs cover less than 4 percent of the quiet surface. The lifetime and degree of packing of BPs vary with the local strength of the magnetic field.

Cook, J. W.↗

NASA NTRS1983

Analysis of coolant entrance boundary shape of porous region to control cooling along exit boundary

A cooled porous region has a plane surface exposed to a specified spatially varying heat flux. The coolant leaves the region through this surface, and it is desired to control the flow distribution to maintain a specified uniform surface temperature. This is accomplished by having the coolant entrance surface shaped to provide in the region the necessary variation of path length and, hence, flow resistance. The surface shape at the coolant entrance is found by solving a Cauchy boundary value problem. An exact solution is obtained that will deal with a wide variety of heating distributions for both two- and three-dimensional shapes.

Siegel, R.↗

NASA NTRS1983

An iterative approach to region growing using associative memories

Region growing, often given as a classical example of the recursive control structures used in image processing which are often awkward to implement in hardware where the intent is the segmentation of an image at raster scan rates, is addressed in light of the postulate that any computation which can be performed recursively can be performed easily and efficiently by iteration coupled with association. Attention is given to an algorithm and hardware structure able to perform region labeling iteratively at scan rates. Every pixel is individually labeled with an identifier which signifies the region to which it belongs. Difficulties otherwise requiring recursion are handled by maintaining an equivalence table in hardware transparent to the computer, which reads the labeled pixels. A simulation of the associative memory has demonstrated its effectiveness.

Snyder, W. E.↗

NASA NTRS1983

Outer atmospheres of cool stars. XIV - A model for the chromosphere and transition region of Beta Ceti (G9.5 III)

In the present chromospheric and transition region model for Beta Ceti, which is consistent with IUE spectra of the Mg II, C II, and C IV resonance lines, the Mg II h and k lines are treated in partial redistribution and the C II and C IV lines in complete redistribution. Computed line fluxes are presented for a range of models to show the range of permitted temperature structures. A comparison of the Beta Ceti model to models previously computed in a similar way for other stars shows a trend of decreasing chromospheric pressures and increasing geometric scales as single stars evolve across the transition region boundary. The present analysis also suggests that transition region pressures drastically decrease and geometric scales rapidly increase as single giant stars evolve to the right, toward the boudnary. Beta Ceti's exceptional X-ray brightness is discussed.

Eriksson, K.↗

NASA NTRS1983

Properties of material in the submillimeter wave region (instrumentation and measurement of index of refraction)

The Properties of Materials in the Submillimeter Wave Region study was initiated to instrument a system and to make measurements of the complex index of refraction in the wavelength region between 0.1 to 1.0 millimeters. While refractive index data is available for a number of solids and liquids there still exists a need for an additional systematic study of dielectric properties to add to the existing data, to consider the accuracy of the existing data, and to extend measurements in this wavelength region for other selected mateials. The materials chosen for consideration would be those with useful thermal, mechanical, and electrical characteristics. The data is necessary for development of optical components which, for example, include beamsplitters, attenuators, lenses, grids, all useful for development of instrumentation in this relatively unexploited portion of the spectrum.

Lally, J.↗

NASA NTRS1984

Auroral kilometric radiation: Wave modes, harmonic and source region electron density structures

A change from extraordinary (X) mode to ordinary (0) mode dominance is observed in the auroral kilometric radiation (AKR) detected on ISIS 1 topside sounder ionograms as the source region plasma to gyrofrequency ratio fN/fH varies from 0.1 to 1.3. The X and 0 mode AKR, Z (the slow branch of the X mode) and whistler (W) mode are also observed. The Z mode is typically slightly less intense than the 0-mode. Thw W-mode is confined to frequencies less than fH/2, suggesting that it is the result of field aligned ducted signals reaching the satellite from a source at lower altitudes. Harmonic AKR bands are commonly observed and the 2nd harmonic appears to be due to propagating signals. The deduced (fN/fH) at the bottom of the AKR source region is always less than 0.4 and is typically less than 0.2 during the generation of X-mode AKR, but approaches 0.9 for 0-mode AKR. No large density enhancements were observed within AKR source region density cavities. It is suggested that the observed INTENSE AKR IS cyclotron X-mode radiation rather than plasma frequency 0-mode radiation.

Benson, R. F.↗

NASA NTRS1984

The energetics and mass structure of regions of star formation: S201

Theoretical predictions about dust and gas in star forming regions are tested by observing a 4 arcmin region surrounding the radio continuum source in 5201. The object was mapped in two far infrared wavelengths and found to show significant extended emission. Under the assumption that the molecular gas is heated solely via thermal coupling with the dust, the volume density was mapped in 5201. The ratios of infrared optical depth to CO column density were calculated for a number of positions in the source. Near the center of the cloud the values are found to be in good agreement with other determinations for regions with lower column density. In addition, the observations suggest significant molecular destruction in the outer parts of the object. Current models of gas heating were used to calculate a strong limit for the radius of the far infrared emitting grains, equal to or less than 0.15 micron. Grains of about this size are required by the observation of high temperature (T equal to or greater than 20 K) gas in many sources.

Thronson, H. A., Jr.↗

NASA NTRS1984

Limits on soft X-ray flux from distant emission regions

The all-sky soft X-ray data of McCammon et al. and the new N sub H survey (Stark et al. was used to place limits on the amount of the soft X-ray diffuse background that can originate beyond the neutral gas of the galactic disk. The X-ray data for two regions of the sky near the galactic poles are shown to be uncorrelated with 21 cm column densities. Most of the observed x-ray flux must therefore originate on the near side of the most distant neutral gas. The results from these regions are consistent with X-ray emission from a locally isotropic, unabsorbed source, but require large variations in the emission of the local region over large angular scales.

Burrows, D. N.↗

NASA NTRS1984

Energy Flow Continuity in Solar Active Regions

The models for sunspots are combined into an active region model with consideration for the energy flow beneath active regions. An apparent average energy balance exists between the sunspot deficit and the facular excess, i.e., no 11 year variations in solar luminosity associated with the activity centers. This is seen as a consequence of the upper convection zone's inability to store these significant amounts of energy for periods greatly in excess of weeks. This view is supported by observed active region behavior and detailed numerical modelling. Increases in facular and spot brightness are nearly commensurate, with the faculae outlasting the spots on time scales of the order of weeks to a couple of months. Foukal finds the radiation (deficit from a sunspot blocking model) recovers slowly on a timescale of approximately 83 days.

Schatten, K. H.↗

NASA NTRS1984

A compilation of mineral occurrences and the relationship of occurrences to structural elements of the Kentucky and Tennessee region

A very prominent magnetic anomaly measured by MAGSAT over the eastern mid-continent of the United States was inferred to have a source region beneath Kentucky and Tennessee. Prominent aeromagnetic and gravity anomalies are also associated with the inferred source region. A crustal model constructed to fit these anomalies interpreted the complex as a large mafic plutonic intrusion of Precambrian age. The complex was named the Kentucky body. It was noticed that the Jessamine Dome, which is a locus of intense faulting and mineralization, occurs near the northern end of the Kentucky body, and that more generally there seemed to be a spatial relationship between mineral occurrence and the body. The relationship between mineral deposits in Kentucky and Tennessee and the Kentucky body was investigated. A compilation of mineral occurrences in the region, classified according to type and age, is presented.

Mayhew, M. A.↗