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  • 1
    Electronic Resource
    Electronic Resource
    Lines of H 2 in extreme-ultraviolet solar spectra (1977)
    [s.l.] : Nature Publishing Group
    Nature 270 (1977), S. 326-327 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] A short stretch of a spectrum obtained with a 51-s exposure time is reproduced in Fig. 1. The top spectrum is of the solar limb, the centre one is of the sunspot and the lower one is of a region of the quiet Sun which contains a small area (2 arc s) in which some of the sunspot lines are greatly ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/270326a0
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  • 2
    Electronic Resource
    Electronic Resource
    Explosive events in the solar transition zone (1989)
    Springer
    Solar physics 123 (1989), S. 41-68 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The properties of explosive events in the solar transition zone are presented by means of detailed examples and statistical analyses. These events are observed as regions of exceptionally high velocity (∼ 100 km s−1) in profiles of Civ, formed at 105 K, observed with the High Resolution Telescope and Spectrograph (HRTS). The following average properties have been determined from observations obtained during the third rocket flight of the HRTS: full width at half maximum extent along the slit - 1.6 × 103 km; maximum velocity - 110 km s−1; peak emission measure - 4 × 1041 cm−3; lifetime - 60 s; birthrate - 4 × 10−21 cm−2 s−1 in a coronal hole and 1 × 10−20 cm−2 s−1 in the quiet Sun; mass - 6 × 108 g; and, kinetic energy - 6 × 1022 erg. The 6 examples show that there are considerable variations from these average parameters in individual events. Although small, the events show considerable spatial structure and are not point-like objects. A spatial separation is often detected between the positions of the red and blue shifted components and consequently the profile cannot be explained by turbulence alone. Mass motions in the events appear to be isotropic because the maximum observed velocity does not show any correlation with heliographic latitude. Apparent motions of the 100 km s−1 plasmas during their 60 s lifetime should be detected but none are seen. The spatial frequency of occurrence shows a maximum near latitudes of 40–50°, but otherwise their sites seem to be randomly distributed. There is enough mass in the explosive events that they could make a substantial contribution to the solar wind. It is hard to explain the heating of typical quiet structures by the release of energy in explosive events.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150011
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  • 3
    Electronic Resource
    Electronic Resource
    A high precision Solar Ultraviolet Spectral Irradiance Monitor for the wavelength region 120–400 nm (1981)
    Springer
    Solar physics 74 (1981), S. 521-530 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract There exists a growing need to improve the accuracy of measurement of the absolute solar flux within the wavelength range 120–400 nm. Although full-disk solar fluxes and variations thereof in the 120–400 nm region are required to model the solar atmosphere, current increased interest in the measurements arises from their importance in modeling the terrestrial atmosphere. We describe the Solar Ultraviolet Spectral Irradiance Monitor (SUSIM) experiment under development at the Naval Research Laboratory (NRL) for flight aboard the Space Shuttle and the Upper Atmospheric Research Satellite (UARS). SUSIM will monitor the solar flux in the 120–400 nm region with high precision, using an in-flight calibration system to reduce absolute error to 〈 10%, and error relative to the 400 nm continuum to 〈 1%.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154535
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  • 4
    Electronic Resource
    Electronic Resource
    Identification of [Fe III ] in the solar ultraviolet spectrum (1986)
    [s.l.] : Nature Publishing Group
    Nature 324 (1986), S. 444-446 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The wavelengths of the emission lines are given in Table 1. Three groups of lines occur, the strongest between 1,575 and 1,598 A, the others between 1,503 and 1,518 A and between 1,431 and 1,452 A. The wavelengths were determined on a scale established from nearby lines of neutral atoms. For the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/324444a0
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  • 5
    Electronic Resource
    Electronic Resource
    Discrete subresolution structures in the solar transition zone (1987)
    Springer
    Solar physics 114 (1987), S. 223-237 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During operations on the Spacelab-2 Shuttle mission, the NRL High Resolution Telescope and Spectrograph (HRTS) recorded spectra of a variety of solar features in the 1200–1700 Å wavelength region which contains spectral lines and continua well suited for investigating the temperature minimum, the chromosphere and transition zone. These data show that, at the highest spatial resolution, the transition zone spectra are broken up from a continuous intensity distribution along the slit into discrete emission elements. The average dimensions of these discrete transition zone structures is 2400 km along the slit, but an analysis of their emission measures and densities shows that the dimensions of the actual emitting volume is conciderably less. If these structures are modelled as an ensemble of subresolution filaments, we find that these filaments have typical radii of from 3 to 30 km and that the cross-sectional fill factor is in the range from 10−5 to 10−2. The transport of mass and energy through these transition zone structures is reduced by this same factor of 10−5 to 10−2 which has significant consequences for our understanding of the dynamics of the solar atmosphere. Because the HRTS transition zone line profiles are not broadened by resolved large-spatial-scale solar velocity fields, the line widths of the Civ lines have been analyzed. The average line width is 0.195 Å (FWHM) and requires an average nonthermal velocity of 16 km s−1 (most-probable) or 19 km s−1 (root-mean-square) which is lower than previously observed values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167342
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  • 6
    Electronic Resource
    Electronic Resource
    A preliminary study of the Extreme Ultraviolet spectroheliograms from Skylab (1973)
    Springer
    Solar physics 33 (1973), S. 265-280 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Some of the first observations obtained with the Naval Research Laboratory's Extreme Ultraviolet Spectrograph (S082A) during the first Skylab mission are presented and compared with magnetograms and other ground-based data. The instrument is a slitless objective-type grating spectrograph covering 170–630 Å and described in Solar Phys. 27, 251 (1972). Chromospheric network, loop prominences, active regions, a flare, limb brightening, XUV bright points, and ‘coronal holes’ are among the phenomena shown and discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152418
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  • 7
    Electronic Resource
    Electronic Resource
    High resolution EUV structure of the chromosphere-corona transition region above a sunspot (1982)
    Springer
    Solar physics 81 (1982), S. 253-280 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Ion emission line intensities between 1170 and 1700 Å allow one to determine the differential emission measure (DEM) and electron pressure of the plasma in the solar transition region (TR). These line intensities together with their Doppler shifts and line widths are measured simultaneously for the first time above a sunsport from data obtained with the NRL High Resolution Telescope and Spectrograph with 0.06 Å spectral and 1″ spatial resolution. The Doppler shifts show both subsonic and supersonic flow in the same line of sight over the umbra. The temperature structure for 40 resolution elements in the sunspot umbra and penumbra is derived from the DEM and the observed electron pressures. Extrapolation of the emission measure curves supports the previous EUV and X-ray observations that coronal plasma above sunspots with T e〉106 K is reduced while emission from TR plasma between 2×105 and 106 K is greatly enhanced relative to quiet or active regions. This enhancement shifts the minimum of the DEM to lower temperatures and increases the slope at 2×105 K by a factor of two. New pressure diagnostics using the emission line intensity ratios of C iv to N iv are presented, and applied to the data. The energy balance in the TR for the sunspot umbra is dominated by radiative losses from the large amount of TR plasma. An estimate of the energy budget shows that an energy input is required to balance the radiative energy losses above the umbra. The observed divergence of the enthalpy flux for the umbral downflows can balance these radiative losses for T e between 30000 and 200 000 K. A typical umbral model of T e versus reduced mass column density is compared with one for chromospheric temperatures determined from the Ca H and K lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151301
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  • 8
    Electronic Resource
    Electronic Resource
    UV observations of macrospicules at the solar limb (1989)
    Springer
    Solar physics 119 (1989), S. 55-63 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract During the Spacelab 2 mission, the NRL High Resolution Telescope and Spectrograph (HRTS) obtained a time-series of broad-band ultraviolet images of macrospicules at the solar limb inside a polar coronal hole with a temporal resolution of 20 and 60 s. The properties of the macrospicules observed in the Spacelab data are measured and compared with the properties reported for EUV macrospicules observed during Skylab (Bohlin et al., 1975; Withbroe et al., 1976). There is a general agreement between the data sets but several differences. Because of the higher temporal resolution of the Spacelab data, it is possible to see macrospicules with shorter lifetimes than seen during Skylab, as well as variations on faster timescales. The largest (30–60′) and fastest (150 km s -1) macrospicules seen during Skylab were not found in the Spacelab observations. The Spacelab data support the conclusion that many macrospicules decay by simply fading away.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146212
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  • 9
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    Explosive events in the solar transition zone (1989)
    Springer
    Details
    Publication Date: 1989-01-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 10
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    Discrete subresolution structures in the solar transition zone (1987)
    Springer
    Details
    Publication Date: 1987-01-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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