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  • 1
    Electronic Resource
    Electronic Resource
    X Rays from the Sun (1969)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 7 (1969), S. 121-148 
    Details
    ISSN: 0066-4146
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.aa.07.090169.001005
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  • 2
    Electronic Resource
    Electronic Resource
    Observation of possible Fe xvii 2p 53p(1S0)-2p 53s(1 P 1, 3 P 1) transitions in spectra of a solar active region and flare (1975)
    Springer
    Solar physics 43 (1975), S. 111-115 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Expected wavelengths and relative intensities are obtained, from calculations of other workers, for the hitherto unobserved transitions 2p 53p(1 S 0)-2p 53s(1 P 1, 3 P 1) in Fe xvii. A candidate pair of lines at 197.05 Å and 242.09 Å was found in laboratory spectra and appears to be present in the spectra of a solar active region observed by the OSO-7 Goddard spectroheliograph, and in the spectrum of a Skylab-observed solar flare.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155148
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  • 3
    Electronic Resource
    Electronic Resource
    OSO-7 results on coronal emission near 304 Å (1975)
    Springer
    Solar physics 43 (1975), S. 337-350 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The spectral composition and spatial distribution of equatorial coronal emission near 304 Å is examined. Spectral scans indicate that the predominant line is from Si xi. Comparisons of observations with calculations of intensity changes with altitude indicate that collisional excitation is important near the Sun but that photoexcitation becomes dominant beyond about 1.3 R ⊙ from the solar center. Observed and calculated intensities are in approximate agreement for abundances and electron densities that are within the range of observed values.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152358
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  • 4
    Electronic Resource
    Electronic Resource
    Energy balance in a magnetically confined coronal structure observed by OSO-7 (1975)
    Springer
    Solar physics 43 (1975), S. 359-376 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A model of a coronal region of enhanced Fexv and Fexvi emission is developed and its energy balance is examined using extreme ultraviolet observations from OSO-7 together with calculations of possible force-free coronal magnetic field configurations. The coronal emissions overlying the photospheric boundary between regions of opposite magnetic polarity are found to be associated with generally non-potential (current-carrying) magnetic fields in the forms of arches with footpoints in regions of opposite polarity. The orientation of these arches relative to the neutral line changes with degree of ionization of the emitting ion (which we infer from our limb observations to be a function of height) and may be evidence of differing electric currents along various field lines. The appearance of a coronal arch, seen side-on, can conveniently be represented by a parabola and a detailed analysis (Appendix) shows this to be a realistic approximation that should be generally useful in analyzing two-dimensional pictures of coronal structures. Applying this analysis to the most prominent coronal region observed in the radiations of Fexv and Fexvi, we find a maximum in the electron temperature, T e , of 2.6 × 106K at the top of arches whose heights are 20000–40000 km and whose footpoints are separated by ≈ 100000 km. A temperature gradient of ▽T e ≈5 × 10-5K cm-1 is found in this coronal structure. Radiative losses are typically fifteen times greater than conductive losses and the energy deposition required to maintain the coronal feature is nearly uniformly distributed along its length.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152360
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    The solar physics Shuttle/Spacelab program and its relationship to studies of the flare build-up (1976)
    Springer
    Solar physics 47 (1976), S. 391-399 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Conclusion The Shuttle/Spacelab program offers an exciting and substantial opportunity for flight of sophisticated instruments for solar research in the 1980's. Problem-oriented missions composed of a number of instruments will be possible as well as flight opportunities for individual instruments developed quickly in response to new knowledge gained from earlier flights. The international scientific community has been asked to participate in defining new facility instruments that are needed. Announcements of Opportunities to participate in the development and use of these instruments will be made by NASA at the appropriate times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152278
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  • 6
    Electronic Resource
    Electronic Resource
    Kα line emission during solar X-ray bursts (1973)
    Springer
    Solar physics 32 (1973), S. 209-225 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Kα X-ray line emission from S, Ar, Ca and Fe is calculated for conditions likely to exist in solar flares. We consider both the non-thermal and thermal phases of flares as indicated by X-ray observations. Impulsive non-thermal events seen at the onset of a flare at photon energies 〉 20 keV generally give rise to small Kα line fluxes (〈250 photons cm-2 s-1) on the basis of data presented by Kane and Anderson. The amount of S Kα radiation in particular depends sensitively on the lower-energy bound of the non-thermal electron distribution giving rise to the impulsive burst, offering a possible means of determining this. Thermal Kα emission is significant for only Fe ions. For S, Ar and Ca, the temperatures required for a sizeable number of electrons with energies greater than the K-ionization potential will also strip these elements to ionization stages too high for Kα transitions to be possible. Comparison of thermal Kα emission from iron during an intense solar flare leads to a very high emission measure on the basis of these calculations, but such a value seems to be compatible with an analysis of the 1–3 Å continuum during the same event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152737
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  • 7
    Electronic Resource
    Electronic Resource
    X-ray and extreme ultraviolet (1–400 Å) spectroscopy of the sun, from OSO-III (1969)
    Springer
    Solar physics 6 (1969), S. 183-192 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract X-ray spectra of the sun have been obtained during solar flares. New emission lines are observed in the spectral range from 1.3 Å to 3 Å, and 8 Å–20 Å, the most intense of the new emission features being tentatively attributed to optical transitions in high stages of ionization of iron (Fexxv through Fexx). Studies of the variability of these lines during flares provide new information of the development of a hot plasma in the initial stages of the flare event.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150943
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  • 8
    Electronic Resource
    Electronic Resource
    A comparison of theoreticalCIV emission line strengths with active region observations obtained with the Solar EUV Rocket Telescope and Spectrograph (SERTS) (1993)
    Springer
    Solar physics 144 (1993), S. 69-74 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Theoretical line ratios involving 2s 2 S - 3p 2 P, 2p 2 P - 3s 2 S, and 2p 2 S - 3d 2 D transitions inCiv between 312 and 420 Å are presented. A comparison of these with solar active region observational data obtained during a rocket flight by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals good agreement between theory and experiment, with discrepancies that average only 22%. This provides experimental support for the accuracy of the atomic data adopted in the line ratio calculations, and also resolves discrepancies found previously when the theoretical results were compared with solar data from the S082A instrument on boardSkylab. The potential usefulness of theCIV line ratios as electron temperature diagnostics for the solar transition region is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667983
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  • 9
    Electronic Resource
    Electronic Resource
    EIT: Extreme-ultraviolet Imaging Telescope for the SOHO mission (1995)
    Springer
    Solar physics 162 (1995), S. 291-312 
    Details
    ISSN: 1573-093X
    Keywords: Solar X-rays ; Solar EUV ; Multilayer telescope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Extreme-ultraviolet Imaging Telescope (EIT) will provide wide-field images of the corona and transition region on the solar disc and up to 1.5 R⊙ above the solar limb. Its normal incidence multilayer-coated optics will select spectral emission lines from Fe IX (171 Å), Fe XII (195 Å), Fe XV (284 Å), and He II (304 Å) to provide sensitive temperature diagnostics in the range from 6 × 104 K to 3 × 106 K. The telescope has a 45 x 45 arcmin field of view and 2.6 arcsec pixels which will provide approximately 5-arcsec spatial resolution. The EIT will probe the coronal plasma on a global scale, as well as the underlying cooler and turbulent atmosphere, providing the basis for comparative analyses with observations from both the ground and other SOHO instruments. This paper presents details of the EIT instrumentation, its performance and operating modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00733432
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  • 10
    Electronic Resource
    Electronic Resource
    On coronal Fe abundances and temperatures from XUV emission lines (1977)
    Springer
    Solar physics 53 (1977), S. 435-444 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract 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 0.3R ⊙ 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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160286
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