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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

The intensities and profiles of XUV transition zone lines in a quiet sun region compared to a polar coronal hole

The intensities of XUV transition-zone lines from limb spectra of a quiet-sun region and a polar coronal hole are compared. The spectra were obtained with a slit spectrograph on Skylab and cover a region from -12 sec within the limb to 20 sec above it. The lines selected for comparison are formed at temperatures that range from 36,000 to 220,000 K. Lines of the higher-temperature ions, e.g. O v, are significantly less intense in the coronal hole, and lines of lower-temperature ions show little change. Profiles of selected optically thin transition-zone lines from the quiet-sun and coronal-hole spectra are also shown. The lines are broader than expected in ionization equilibrium, and bulk-motion velocities are deduced from the widths of the lines. There appears to be little, if any, statistically significant difference in the velocities obtained from the quiet-sun region and the coronal hole.

Feldman, U.↗
NASA NTRS1975

Limb-brightening curves of XUV transition zone lines in the quiet sun and in a polar coronal hole observed from Skylab

Solar limb-brightening curves are discussed for XUV spectral lines formed in the upper chromosphere and transition zone of a quiet region and a polar coronal hole. The spectra were recorded with a slit spectrograph on Skylab. The lines considered are emitted from ions formed within the temperature range from 10,000 to 220,000 K. The limb-brightening curves cover a region from -4 sec within the limb to +20 sec above it. The data from 0 sec to +20 sec are compared with predictions based on both homogeneous and inhomogeneous models of the transition zone. The limb-brightening curve of the O I line at 1355.6 A indicates that O I is formed in spicules. The limb brightening of the He II line at 1640.4 A is consistent with a temperature of formation between about 40,000 and 90,000 K for He II.

Doschek, G. A.↗
NASA NTRS1976

XUV spectrum of C I observed from Skylab during a solar flare

A list of 193 neutral carbon lines observed in the XUV spectrum of a solar flare between 100 and 2000 A using the normal incidence spectrograph flown on Skylab is presented. Of these, 69 are newly identified lines arising from transitions from upper levels of high quantum number where the quantum number is not less than six. The new lines have allowed the determination of 63 new energy levels. Wavelengths for an additional 109 transitions were calculated by polynomial fitting using reference wavelengths of unblended neutral carbon, Si, N, and S lines emitted in the same atmospheric regions of the flare. The calculated lines falling between 1102 and 1140 A were not observed due to low instrumental efficiency at these wavelengths. The calculated wavelengths are in excellent agreement with those of Johansson (1965). It appears that in solar spectra recombination processes are dominant, enhancing the populations of the high quantum levels relative to the populations of levels with small quantum numbers.

Feldman, U.↗
NASA NTRS1977

Optical contamination - Its prevention in the XUV spectrographs flown by the U.S. Naval Research Laboratory in the Apollo Telescope Mount

During construction and testing of the XUV spectrographs flown in the ATM by the Naval Research Laboratory, many problems associated with optical contamination were encountered. Solving these problems required setting up a contamination prevention program to select the materials used in constructing the instruments and to delineate procedures in assembling, testing, and storing the instruments. A brief description is given of methods of assessing the effects of contamination and of the procedures used to prevent contamination.

Hunter, W. R.↗
NASA NTRS1977

On coronal Fe abundances and temperatures from XUV emission lines

Data obtained by the OSO-7 spectroheliograph on strong XUV lines of five different Fe ions from the outer equatorial corona are presented. Interpretation of the data with a spherically symmetric model atmosphere gives average ion abundances for lines of sight at 0.3 solar radii from the limb. Fe XVI is usually more abundant than Fe XV, XIV, XII and IX, but there are times when Fe XII is more abundant than the other ions. The deviation of measured relative abundances of Fe XII, XIV, and XVI from predictions of ionization equilibrium at one temperature seems to indicate that there are appreciable temperature variations along lines of sight. Element abundances are very uncertain since they appear to depend so heavily on likely but unknown density irregularities along lines of sight.

Nakada, M. P.↗
NASA NTRS1979

Line identification and lifetime measurements in the XUV and soft X-ray regions

A summary of the data acquired concerning line identification and lifetime measurements in the xuv and soft X-ray regions for a variety of both resonance transitions and forbidden transitions in ions of astrophysical interest is provided. Particular attention is called to a few papers which appeared in the Astrophysical Journal. These are of special relevance to specific astrophysical data needs. The many experiments completed in areas related to but somewhat outside the confines of the project title are mentioned.

Sellin, I. A.↗
NASA NTRS1978

The XUV spectroheliometer on SMM

The XUV spectroheliometer for the Solar Maximum Mission (SMM) is described. This instrument is a grazing-incidence polychromatic photoelectric spectrometer illuminated by a grazing-incidence telescope mirror. The wavelength range is 20-1336 A, the spectral resolution is between 0.1 and 0.3 A, and the spatial resolution is 4 arcsec. Simultaneous spectroheliograms in twelve spectral lines are obtained by rastering the instrument at variable rates. The scientific objectives and the mission operations concept are also described.

Reeves, E. M.↗
NASA NTRS1980

CCD camera systems and support electronics for a White Light Coronagraph and X-ray XUV solar telescope

Two instruments, a White Light Coronagraph and an X-ray XUV telescope built into the same housing, share several electronic functions. Each instrument uses a CCD as an imaging detector, but due to different spectral requirements, each uses a different type. Hardware reduction, required by the stringent weight and volume allocations of the interplanetary mission, is made possible by the use of a microprocessor. Most instrument functions are software controlled with the end use circuits treated as peripherals to the microprocessor. The instruments are being developed for the International Solar Polar Mission.

Harrison, D. C.↗
NASA NTRS1980

Spatial distribution of XUV emission and density in a loop prominence

The spatial distribution of XUV emission in the 14 August, 1973 loop prominence observed with the NRL spectroheliograph on Skylab is studied. The loop prominence consists of two large loops and is observed in lines from ions with temperatures ranging from 50,000 to 3,000,000 K. The loops seen in low temperature lines such as from He II, Ne VII, Mg VII, Mg VIII, and Si VIII are systematically displaced from loops seen in higher temperature lines such as from Si XII, Fe XV, and Fe XVI. The cross section of the loop, particularly in cooler lines is nearly constant along the loop. For hotter loops in Si XII, Fe XV, and Fe XVI, however, emission at the top of the loop is more intense and extended than that near the footpoints, which makes the loops appear wider at the top. The observed spatial displacement between cooler and hotter loops suggest that the 14 August loop prominence is composed of many magnetic flux tubes, each with its own temperature.

Cheng, C.-C.↗
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 NTRS1981

A systems approach to mechanisms for a white light coronagraph X-ray XUV telescope

A combined instrument package containing nine mechanisms was designed and developed for the international solar polar mission (ISPM). This complement of instruments, commonly called the CXX, is the only imaging system on either the NASA or ESA spacecraft and consists of a white light coronagraph mounted parallel to a combined X-ray and extreme ultra-violet (XUV) telescope. Requirements for and implementation of mechanisms in the CXX instrument are discussed.

R Mastronardi↗
NASA NTRS1981

Photoelectric array detectors for use at XUV wavelengths

The characteristics of photoelectric detector systems for use at visible-light, ultraviolet, and X-ray wavelengths are briefly reviewed in the context of the needs of the Spacelab solar-physics facilities. Photoelectric array detectors for use at XUV wavelengths between 90 and 1500 A are described, and their use in the ESA Grazing-Incidence Solar Telescope (GRIST) facility is discussed.

Timothy, J. G.↗
NASA NTRS1983

Spontaneous Raman scattering as a high resolution XUV radiation source

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a cw hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated.

Rothenberg, J. E.↗
NASA NTRS1982

Solar EUV, XUV and soft X-ray telescope facilities

Facility class, high resolution instrumentation can enable maximum spatial, spectral and temporal resolutions and provide understanding of the complex physical conditions in the outer solar atmosphere and the mechanisms responsible for these conditions. The scientific rationale for facility class instruments operating in the EUV, XUV, and soft X ray spectral ranges are discussed. Possible configurations for these facilities and priorities for their development are considered.

Withbroe, G. L.↗
NASA NTRS1983

Spontaneous Raman scattering as a high-resolution XUV radiation source

A type of high resolution XUV radiation source is described which is based upon spontaneous anti-Stokes scattering of tunable incident laser radiation from atoms excited to metastable levels. The theory of the source is summarized and two sets of experiments using He (1s2s)(1)S atoms, produced in a CW hollow cathode and in a pulsed high power microwave discharge, are discussed. The radiation source is used to examine transitions originating from the 3p(6) shell of potassium. The observed features include four previously unreported absorption lines and several sharp interferences of closely spaced autoionizing lines. A source linewidth of about 1.9 cm(-1) at 185,000 cm(-1) is demonstrated. Previously announced in STAR as N83-18422

Rothenberg, J. E.↗
NASA NTRS1986

XUV radiometric standards at NBS

The far-UV and XUV detector calibration services at NBS, the properties of the detectors, and the spectrometer calibration facilities at the Synchrotron Ultraviolet Radiation Facility (SURF II) at NBS are described. The method used to calibrate the quantum efficiency of windowless photodiode detectors in the ionization chamber, and the facilities for calibrating photodiodes at various wavelengths are discussed. The cathode and anode of the windowless photodiodes and their operation are examined. Consideration is given to the calculation of spectral irradiance from SURF II; the two stations of the spectrometer facility; the large spectrometer calibration chamber; and sources of error in flux determinations for SURF II.

Ott, W. R.↗
NASA NTRS1988

Monochromatic X-ray and XUV imaging with multilayer optics

The development of techniques for the fabrication of multilayer coated mirrors which can function as energy selective X-ray and XUV mirrors at normal incidence has greatly expanded the options available to the astronomical spectroscopist. A rocket spectroheliograph which utilizes multilayer optics in three configurations has been developed. These are: (1) as Cassegrain telescopes for imaging at 256 A (He II) and 173 A (Fe IX, X); (2) as tertiary mirrors used with a conventional Wolter I telescope for imaging at 44 A (Si XI, XII), 173 A, and 256 A; and (3) as off-axis spherical mirrors for imaging at 44 A and 256 A. The paper reports on laboratory images and performance measurements obtained with these optical systems, and briefly on Solar Observations.

Walker, A. B. C., Jr.↗
NASA NTRS1990

The ultra high resolution XUV spectroheliograph: An attached payload for the Space Station Freedom

The principle goal of the ultra high resolution XUV spectroheliograph (UHRXS) is to improve the ability to identify and understand the fundamental physical processes that shape the structure and dynamics of the solar chromosphere and corona. The ability of the UHRXS imaging telescope and spectrographs to resolve fine scale structures over a broad wavelength (and hence temperature) range is critical to this mission. The scientific objectives and instrumental capabilities of the UHRXS investigation are reviewed before proceeding to a discussion of the expected performance of the UHRXS observatory.

Walker, Arthur B. C., Jr.↗