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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The effect of suprathermal protons on the physical conditions in Seyfert galaxy nuclei

The physical conditions in a high density hydrogen gas heated and ionized by suprathermal protons were investigated, with application to the gas in the nuclear region of Seyfert galaxies. The gas is assumed optically thick to Lyman and Balmer line radiation. Mechanisms by which the radiation from the gas can balance the heating by the fast protons were investigated, and minimum values for the mass of gas were estimated. Under certain conditions, the suprathermal atoms themselves can cool the ambient gas by rescattering the line radiation into the optically thin region in the wings of the line. This mechanism, called optical reverberation, can enhance the broad component of the hydrogen lines produced by inelastic atomic collisions and yield line widths consistent with those observed in Seyfert and quasar spectra. Also discussed is the possibility of achieving dynamic equilibrium of the ambient gas by balancing the momentum transfer from the suprathermals with gravitational attraction of a massive central source.

Ptak, R.↗
NASA NTRS1975

The shape of the sodium D lines in a high-temperature helium atmosphere

An experiment was performed to measure the shape of the sodium resonance doublet (lambda 5890, lambda 5896) in a high-temperature helium atmosphere. A piston compressor was used to produce temperatures in the range 3000 K to 5500 K. Absorption-line widths and shifts are reported and the widths agree well with calculations.

Eckart, M. J.↗
NASA NTRS1975

High dispersion observations of Venus during 1972 - The CO2 band at 7820 A

Results are reported for analysis of 47 photographic plates of Venus which show the spectrum of the CO2 band at 7820 A. Evidence is found for a semiregular four-day variation in the CO2 abundance over the disk of the planet as well as for temporal variations in the rotational temperature of the 7820-A band and temperature variations over the disk. No apparent relationship is found between the CO2 abundance and temperature, although an increase in temperature is usually accompanied by a decrease in the CO2 abundance. A curve-of-growth analysis assuming a constant CO2 line width yields an average rotational temperature of about 249 K, which is several degrees higher than previously obtained rotational temperatures for the same band. Temperature variations are found to indicate that the average temperature in the equatorial and polar regions is 2.3 K higher than that near the limb or terminator.

Young, L. D. G.↗
NASA NTRS1975

A model for Io's atmosphere and sodium cloud

Observations of the sodium D-line emissions associated with the Galilean satellite Io suggest that the emitting region has two components. The first is an atmosphere which extends 1000 km above Io's surface. This is a relatively dense region which is optically thick in the sodium D lines. The second component is a surrounding optically thin cloud spread out along Io's orbit to form part of a torus. No emission was detected during any of three eclipses observed, although Io's sodium emission was consistently present when Io was near orbital elongation. This indicates that resonant scattering is the principal emission mechanism in both components. For the atmosphere, measurements of the D-line intensity, D-2/D-1 ratio, and line width indicate a temperature of 500 to 1000 K and a sodium column abundance of 3 by 10 to the 13th power per sq cm. Upper limits to the abundance of Mg, K, Ca, and Li indicate a high sodium abundance ratio in the atmosphere. This may also be true for Io's surface if sputtering by energetic particles is the source of the atmosphere. The sodium cloud has been detected as far as 60 arcsec from Io in the orbital plane and at least 6 arcsec above and below this plane. The cloud can be sustained by atoms escaping from the critical level at the top of the atmosphere.

Macy, W., Jr.↗
NASA NTRS1975

The effect of suprathermal protons on the physical conditions in Seyfert galaxy nuclei

Physical conditions in a high-density hydrogen gas heated and ionized by suprathermal protons are investigated, and the results are applied to the gas in the nuclear region of Seyfert galaxies. The gas is assumed to be optically thick to Lyman and Balmer line radiation. Mechanisms by which the radiation from the gas can balance the heating by the fast protons are investigated, and minimum values for the mass of gas are estimated. Under certain conditions, the suprathermal atoms themselves can cool the ambient gas by rescattering the line radiation into the optically thin region in the wings of the line. This mechanism, optical reverberation, can enhance the broad component of the hydrogen lines produced by inelastic atomic collisions and yield line widths consistent with those observed in Seyfert and quasar spectra. If this mechanism is important, the Lyman decrement can depend strongly on the temperature and density of the ambient hydrogen. The possibility is discussed of achieving dynamic equilibrium of the ambient gas by balancing the momentum transfer from the suprathermals with gravitational attraction of a massive central source.

Ptak, R.↗
NASA NTRS1976

Reflected-wave maser

A number of traveling-wave, slow-wave maser structures, containing active maser material but absent the typical ferrite isolators, are immersed in a nonuniform magnetic field. The microwave signal to be amplified is inserted at a circulator which directs the signal to a slow-wave structure. The signal travels through the slow-wave structure, being amplified according to the distance traveled. The end of the slow-wave structure farthest from the circulator is arranged to be a point of maximum reflection of the signal traveling through the slow-wave structure. As a consequence, the signal to be amplified traverses the slow-wave structure again, in the opposite direction (towards the circulator) experiencing amplification equivalent to that achieved by a conventional traveling-wave maser having twice the length. The circulator directs the amplified signal to following like stages of amplification. Isolators are used in between stages to prevent signals from traveling in the wrong direction, between the stages. Reduced signal loss is experienced at each stage. The high gain produced by each slow-wave structure is reduced to a moderate value by use of a nonuniform magnetic field which also broadens the line width of the maser material. The resulting bandwidth can be exceptionally wide. Cascaded stages provide high gain, exceptionally wide bandwith and very low noise temperature.

Clauss, R. C.↗
NASA NTRS1975

Comment on resonance broadening

The conflicting results describing the relationship between line width and absorber density in resonance broadening are considered. A reexamination of some of these experiments points to a common difficulty - large optical depth. Formulas are given which approximate the widths and dependencies observed under optically thick conditions. It is concluded that a resonance breadth which is linear with density is consistent with all of the observations and that there is no solid basis for a square root dependence at low density.

Exton, R. J.↗
NASA NTRS1977

Automated array assembly task, phase 1

Various aspects of a sensitivity analysis, in particular, the impact of variations in metal sheet resistivity, metal line width, diffused layer sheet resistance, junction depth, base layer lifetime, optical coating thickness and optical coating refractive index and on process reproducibility for A's diffusion from a polymer dopant source and on module fabrication were studied. Model calculations show that acceptable process windows exist for each of these parameters.

Carbajal, B. G.↗
NASA NTRS1976

Ozone spectroscopy with a CO2 waveguide laser

Ozone spectral measurements were conducted with a waveguide CO2 laser, which was continuously tunable over a + or - 450-MHz region, about several lines in the P-branch of the band near the 9.5-micron wavelength region. A passively stabilized low-pressure CO2 laser was also used to provide reference CO2 frequencies. The frequencies of several ozone lines were determined in the nu-3 band, which are near CO2 laser line frequencies in the 9.5-micron wavelength region. The absolute measurement accuracy is estimated to be + or - 6 MHz, and the measurements indicate that the ozone line frequencies listed in currently available spectral compilations are 0.003-0.006 per cm too high. The size of this error is small by conventional IR standards, but extremely important when CO2 laser instruments are used to monitor stratospheric ozone, where line widths in this spectral region are typically 0.001/cm. Empirically determined absorption curves must be constructed in order to calibrate laser differential absorption instrument properly when low-altitude ozone measurements are conducted.

Menzies, R. T.↗
NASA NTRS1977

The Lyman alpha coronagraph

The rocket-borne Lyman alpha coronagraph (RLAC) is to be used in the absence of a natural solar eclipse to determine coronal temperatures from measurements of the line width of Lyman-alpha and to determine neutral hydrogen densities of coronal material from the absolute intensity. The coronagraph consists of a 75-cm Fastie-Ebert scanning spectrometer with an AMR 641 photoelectric detection system, an off-axis parabolic primary mirror, and an occulting system. A special optical arrangement achieves rejection of radiation from the solar disk.

Kohl, J. L.↗
NASA NTRS1977

Evolution of the high-temperature plasma in the 15 June 1973 flare

The evolution of the high-temperature plasma in the solar flare of June 15, 1973, is analyzed using XUV spectroheliograms obtained from Skylab. Preflare enhancement of loops in the active region is discussed, and the temperature and density of the hot plasma are determined as a function of time. The turbulent velocity in the high-temperature plasma is deduced from a comparison of line widths of the Fe XXIV doublet at 192 and 255 A. The results indicate that: (1) the flare occurred in a low-lying loop or loops; (2) the large-scale magnetic-field configuration of the active region did not change significantly; (3) the hot plasma observed in Fe XXIII-XXIV showed considerable dynamic activity, including an initial upward motion of the whole plasma with a velocity of about 80 km/s; (4) large turbulent mass motions took place in the Fe XXIII-XXIV plasma with random velocities of 100 to 160 km/s; (5) the temperature of the hot plasma was 14 million K at peak X-ray intensity, decreased slightly, and then remained at 12.6 million K before dropping to below 10 million K; and (6) there was a temperature gradient along the length of the loop, with the 14 million-K plasma near the top and progressively lower-temperature plasmas on either side.

Cheng, C.-C.↗
NASA NTRS1978

IUE observations of cool stars - Alpha Aurigae, HR1099, Lambda Andromedae, and Epsilon Eridani

Initial IUE observations of four cool stars are reported. Observed fluxes and surface fluxes are given for several UV emission lines in the spectral range 1175-2000 A, obtained at low and high dispersion with the short-wavelength spectrograph and camera. These lines are formed in the outer atmospheres of these stars, in regions presumably analogous to the solar chromosphere and transition region. The surface fluxes in the lines increase along the sequence: quiet sun, Epsilon Eri, Lambda And, Alpha Aur, and HR1099. The 2.8-d RS CVn-type binary HR1099, observed on 1 March 1978 near the end of a major flaring episode, has line surface fluxes roughly 100 times that of the quiet sun, similar to those seen in solar flares. Line profiles and flux ratios in multiplets for Capella are presented, and comments given on the opacity of the lines and on a tendency of line width to increase with temperature of formation.

Linsky, J. L.↗
NASA NTRS1980

improving maser frequency stability

Hydrogen maser frequency standard is more stable by addition of parallel pyrex capillary tube array collimator. With collimator, maser line width has been made as narrow as 0.24 hertz representing fivefold improvement over maser without collimator. Fluorocarbon coating in tubes virtually eliminates energy loss in collimator.

Crampton, S. B.↗
NASA NTRS1979

Molecules of significance in planetary aeronomy

This monograph is basically devoted to spectroscopic information of the molecules of planetary interest. Only those molecules have been dealt with which have been confirmed spectroscopically to be present in the atmosphere of major planets of our solar system and play an important role in the aeronomy of the respective planets. An introduction giving the general conditions of planets and their atmospheres including the gaseous molecules is given. Some typical planetary spectra is presented and supported with a discussion on some basic concepts of optical absorption and molecular parameters that are important to the study of planetary atmospheres. Quantities like dipole moments, transition probabilities, Einstein coefficients and line strengths, radiative life times, absorption cross sections, oscillator strengths, line widths and profiles, equivalent widths, growth curves, bond strengths, electronic transition moments, Franck-Condon factors and r-centroids, etc., are discussed. Spectroscopic information and relevant data of 6 diatomic (HF, HCL, CO, H2, O2, N2) and 6 polyatomic (CO2, N2), O3, HeO, NH3, CH4) molecules are presented.

Mohan, H.↗
NASA NTRS1978

Voltage tunable differential heterodyne spectroscopy in the far-infrared with Josephson junctions

The basic methods of differential heterodyne spectroscopy with Josephson junctions are described. A technique is outlined for bridging the gap between a local oscillator frequency and a signal frequency through the use of a voltage-tunable internal oscillation frequency in a Josephson junction structure. It is shown that an intermediate frequency can be converted to a conveniently low frequency by double frequency conversion carried out directly in a Josephson junction. The expected conversion efficiency is estimated qualitatively. Experiments are discussed in which the differential heterodyne frequency-conversion technique was demonstrated at a wavelength of 0.4 mm and a voltage-tunable oscillation in a double Josephson junction structure was observed, with oscillation line widths as narrow as 0.5 Hz, for a resistance of 3.3 nanohms and an estimated inductance of the order of 1 nH.

Ulrich, B. T.↗
NASA NTRS1979

Jovian sodium emission from Region C2

Observations of emission from sodium presumed to have been ejected from Io in the orbital plane of the Gallilean satellites and extending outward to at least 35 Jupiter radii are reported. Spectra of the sodium D line were observed to have an intensity of 20 to 30 R. Mechanisms for the escape of sodium from Io after sputtering from the surface are: (1) ejection from Io at velocities greater than Jupiter escape velocity, (2) ejection at velocities corresponding to orbits with apoapses of 35 Jupiter radii, and (3) ionization followed by magnetic field sweeping and recombination. The relative contributions of each mechanism are estimated and used to predict the sodium emission intensity at 35 Jupiter radii to be 7 to 8 R, a value considered to be in reasonable agreement with observations. Observations of emission line width and the correlation of intensity with the orbital phase of Io would provide further means of evaluating the proposed mechanisms of sodium ejection.

Pilcher, C. B.↗
NASA NTRS1979

Gyroharmonic emissions induced by energetic ions in the equatorial plasmasphere

A theoretical investigation shows that MeV ions observed in the plasmasphere which have a power law distribution function possessing strong pitch angle anisotropy can give rise to emissions at frequencies near the harmonics of the ion gyrofrequencies observed in the same region. These emissions are sustained by the low-beta sub c plasma in the plasmasphere. It is found that only emissions with frequencies along the fast magnetosonic branch may occur and that these waves are essentially perpendicularly propagating. Growth is restricted to frequencies immediately below the ion gyroharmonics by the resonance condition and implies line widths of about 0.001 Omega sub alpha. Observations of ion gyroharmonic emissions with spacings of 1/16, 1/8, and 3/16 of the proton gyrofrequency may indicate the existence of energetic ion O(+), O(2+), and O(3+), respectively.

Curtis, S. A.↗
NASA NTRS1979

An atomic model for neutral and singly ionized uranium

A model for the atomic levels above ground state in neutral, U(0), and singly ionized, U(+), uranium is described based on identified atomic transitions. Some 168 states in U(0) and 95 in U(+) are found. A total of 1581 atomic transitions are used to complete this process. Also discussed are the atomic inverse lifetimes and line widths for the radiative transitions as well as the electron collisional cross sections.

Maceda, E. L.↗