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  • 1
    Electronic Resource
    Electronic Resource
    The Effects of Departures from LTE in Stellar Spectra (1973)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 11 (1973), S. 187-218 
    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.11.090173.001155
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    A first order analysis of variations of the limb darkening and the shapes for solar Fraunhofer lines (1972)
    Springer
    Solar physics 24 (1972), S. 18-27 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New center-to-limb measurements in FeI lines show changes in both the line profiles and the limb darkening curves that appear to be characteristic of many other solar lines. Here we seek the constraints placed on the atmospheric model by these effects. We find that in addition to a depth varying source function we must also allow the ratio of the continuous absorption coefficient to the total absorption coefficient to pass through a minimum in the mid-photosphere. Such an effect is consistent with inward increases of the Doppler width and damping constant in the upper photosphere and an inward increase of the ionization for both iron and hydrogen in the low photosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231078
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Hydrogen ionization and n=2 population for model spicules and prominences (1971)
    Springer
    Solar physics 18 (1971), S. 391-402 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using slab model atmospheres that are irradiated from both sides by photospheric, chromospheric, and coronal radiation fields we have determined the ionization and excitation equilibrium for hydrogen. The model atom consists of two bound levels (n = 1 and n = 2) and a continuum. Ly-α was assumed to be optically thick with the transition in detailed radiative balance. The Balmer continuum was assumed to be optically thin with the associated radiative ionization dominated by the photospheric radiation field (T rad = 5940 K). The ionization equilibrium was determined from an exact treatment of the radiative transfer problem for the internally generated Ly-c field and the impressed chromospheric and coronal field (characterized by T rad = 6500K). Our calculations corroborate the hypothesis that N2, the n = 2 population density, is uniquely determined by the electron density 〈N e〉. We also present ionization curves for 6000K, 7500K, and 10000K models ranging in total hydrogen density from 1 × 1010/cm3 to 3 × 1012/cm3. Using these curves it is possible to obtain the total hydrogen density from the n = 2 population density in prominences and spicules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149061
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    SMM/UVSP observations of the distribution of transition region oscillations and other properties in a sunspot (1984)
    Springer
    Solar physics 91 (1984), S. 33-44 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of a sunspot in the Civ line at 1548 Å formed in the transition region have been analyzed to obtain the time variations and/or mean values of the velocity, intensity, longitudinal magnetic field, and line width. Oscillations with periods between approximately 110 and 200 s are observed only over the umbra where the transition region magnetic field is highest and the line width is smallest. When periodic intensity variations occur at the same frequency as the velocity oscillations, the peak intensities occur slightly before the maximum upward motions. No periodic variations in the transition region magnetic field have been detected. Scatter diagrams are presented which show possible relationships between the flow velocity, emission line intensity, line width, and transition region magnetic field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213608
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Downflows in coronal loops (1987)
    [s.l.] : Nature Publishing Group
    Nature 327 (1987), S. 685-687 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] To establish this conclusion, we first review the observed properties of commonly occurring flows. Three features of the flow that have been extensively documented are as follows. (1) The apparent downflow velocity1'2 reaches a maximum near 105 K and is markedly diminished near 2 x 105 K. (2) An ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/327685a0
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  • 6
    Electronic Resource
    Electronic Resource
    Characteristics of the expansion associated with eruptive prominences (1987)
    Springer
    Solar physics 110 (1987), S. 359-379 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Gradients of Hα and electron scattering intensities derived from instantaneous radial distributions of erupting prominence material observed at several solar radii by Illing and Athay (1986) are often markedly smaller than those inferred by comparing the intensities observed near several radii to average prominence intensities observed near the limb. In this paper, we show that gradients derived by following individual features in their outward progression with time yield values that are consistent with limb observations and that usually exceed the values obtained from instantaneous distributions. We conclude from the diversity of observed gradients that the prominence eruption cannot be described by a self-similar expansion in which the expansion velocity is a function of radius and time only. However, we cannot rule out possible self-similar solutions that allow the expansion velocity to be a function of angular direction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00206431
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Velocity effects on the profiles of Hα and two FeI lines (1970)
    Springer
    Solar physics 12 (1970), S. 175-185 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Profiles are computed for Ha and two Fei lines for a differentially moving atmosphere. The results show that the profiles are asymmetric and that velocity measurements made in the Doppler cores will often lead to erroneous results when the velocity gradient is significant in the regions of the atmosphere where the core forms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00227116
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    Solar EUV emission line profiles of Si ii and Si iii and their center to limb variations (1977)
    Springer
    Solar physics 55 (1977), S. 305-319 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Spectral line profiles of Si ii and Si iii are presented which were observed both at solar center and near the quiet solar limb with the Naval Research Laboratory EUV spectrograph of ATM/SKYLAB. Absolute intensities and line profiles are derived from the photographic data. A brief discussion is given of their center-to-limb variations and of the optical thickness of the chromosphere in these lines. Nonthermal broadening velocities are found for the optically thin lines from their full width at half maximum intensity (FWHM).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152575
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    Paper (German National Licenses)
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