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  • 1
    Electronic Resource
    Electronic Resource
    Rocket and Satellite Observations of the Solar Ultra-violet Spectrum (1960)
    [s.l.] : Nature Publishing Group
    Nature 186 (1960), S. 1036-1036 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Rocket and satellite programmes are under way for the continuous monitoring of the energy -flux and the accurate determination of the profiles of the Lyman-oc lines. It is the purpose of this communication to direct attention to the unusual importance of parallel observations of the Lyman-p lines. ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/1861036a0
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  • 2
    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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  • 3
    Electronic Resource
    Electronic Resource
    Automated and graphical methods for locating heavy-atom sites for isomorphous replacement and multiwavelength anomalous diffraction phase determination (1998)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 31 (1998), S. 270-274 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: We have developed new software for locating heavy-atom sites for phase determination from single isomorphous replacement (SIR) and multiwavelength anomalous diffraction (MAD) data. The first component of the software is a program for finding heavy-atom sites when presented with SIR (i.e. native and derivative) structure-factor amplitudes or MAD-FA structure-factor amplitudes (i.e. the derived structure factors corresponding to the anomalously scattering atoms). The principle on which this program is based is a reciprocal-space maximization of a Patterson correlation coefficient between the SIR or MAD-FA data and the calculated intensities from search atoms placed at trial positions. The program has been successfully tested on two sets of SIR data for the cytochrome c′ protein and on MAD-FA data from the DnaK protein. The second component of the software is a three-dimensional viewer which may be used to assess difference Patterson maps and which provides peak-picking and atom-editing facilities for interpreting cross-difference Fourier maps.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889897013253
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  • 4
    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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  • 5
    Electronic Resource
    Electronic Resource
    Theoretical chromospheric flare spectra (1974)
    Springer
    Solar physics 34 (1974), S. 193-206 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We simultaneously solve the equations of radiative transfer and statistical equilibrium for a model hydrogen atom including Lyman-α, Lyman-β, Balmer-α and the Lyman, Balmer and Paschen continua. The model atmospheres we use are the results of Nakagawa et al. (1973) for a kinematic model of the chromospheric solar flare. We find that the models adequately predict the total intensity of Bα, its wing broadening, the presence of a red-shifted wing, the maximum electron density, the total line-of-sight second-level population and the narrowness in height of the Bα emitting region. The profile of Bα is strongly self-reversed, however, and agrees with observations only in the presence of 40–70 km s−1 macroturbulent motion. We find that Nakagawa et al. (1973) seriously overestimate the radiative loss function, which will have a large effect on their models. Proper radiative loss calculations must be included in any physically realistic model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149612
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  • 6
    Electronic Resource
    Electronic Resource
    Coronal density and temperature gradients (1973)
    Springer
    Solar physics 29 (1973), S. 357-364 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mean density models of the solar corona show evidence for two distinctive density regimes characterized by different density gradients. High density gradients are identified with regions of predominantly open magnetic lines of force and low density gradients are identified with regions of predominantly closed magnetic lines of force. Spectroscopic data yielding equivalent widths of forbidden lines of Fe x and Fe xiv strongly suggest that the coronal temperature for r 〉 2.5 R ⊙ decreases considerably less rapidly in equatorial regions than r −2/7, which is the decrease predicted by conduction models with open field lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150813
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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Emission cores in H and K lines (1968)
    Springer
    Solar physics 4 (1968), S. 176-184 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Calculations are made for the center-limb variations of the K2 and K3 components of the solar Ca ii K line using an optically thick model of the chromosphere. The center-limb variations are shown to require an increase of Doppler width with height in the chromosphere and to depend critically upon the location of the point where Δλ D has increased by a factor e. Good agreement with observations is found when, and only when, the increase in Δλ D occurs nearly simultaneously with the increase in chromospheric temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148079
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  • 9
    Electronic Resource
    Electronic Resource
    An archetype hydrogen atmosphere problem (1975)
    Springer
    Solar physics 45 (1975), S. 15-23 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Populations for the first three bound states and the continuum of hydrogen are determined for an isothermal, hydrostatic atmosphere at 20 000 K. The atmosphere is treated as being optically thin in the Balmer and Paschen continua and illuminated by continuum radiation at these wavelengths with prescribed radiation temperatures. The atmosphere is optically thick in the 2-1, 3-1, 3-2 and c-1 transitions. Three stages of approximation are treated: (1) radiative detailed balance in the 2-1, 3-1 and 3-2 transitions, (2) radiative detailed balance in the 3-1 and 3-2 transitions, and (3) all transitions out of detailed balance. The solution of this problem is non-trivial, and presents sufficient difficulty to have caused failure of at least one rather standard technique. The problem is thus a good archetype against which new methods, or new implementations of old methods may be tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152212
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  • 10
    Electronic Resource
    Electronic Resource
    Vector magnetic fields in prominences (1983)
    Springer
    Solar physics 89 (1983), S. 3-30 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations of linear polarization in two resolved components of HeI D3 are interpreted using the Hanle effect to determine vector magnetic fields in thirteen prominences. As in all vector magnetic field measurements, there is a two-fold ambiguity in field direction that is symmetric to a 180° rotation about the line-of-sight. The polar angles of the fields show a pronounced preference to be close to 90° from the local solar radius, i.e., the field direction is close to horizontal. Azimuth angles show internal consistency from point to point in a given prominences, but because of the rotational symmetry, the fields may be interpreted, in most cases, as crossing the prominence either in the same sense as the underlying photospheric fields or in the opposite sense. An exceptionally well observed large prominence of approximately planar geometry exhibits no measurable change in the vector magnetic field either with height or with location along the prominence axis. A second well observed large prominence overlying a sharply curved magnetic neutral line, when interpreted assuming that the prominence field has the same sense as the photospheric field, shows a rotation in the azimuth angle of the field relative to the observer by about 150° and relative to the local plane of the prominence by about 65°. In the alternative interpretation in which the prominence field has the opposite sense of the photospheric field, the field still rotates by 150° relative to the observer but remains essentially constant with respect to the plane of the prominence. This prominence erupted shortly after the extended observations. One good quality observation during the course of the eruption gives a vector field fully consistent with the pre-eruption field in the same segment of the prominence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211948
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