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  • Articles: DFG German National Licenses  (14)
Source
  • Articles: DFG German National Licenses  (14)
Material
Years
  • 1
    Electronic Resource
    Electronic Resource
    Bright rings around sunspots (1999)
    [s.l.] : Macmillian Magazines Ltd.
    Nature 401 (1999), S. 678-679 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] There are two possible explanations for why sunspots are dark: the partial suppression by the sunspot magnetic fields of convective energy transport from the underlying layers, or the removal of energy from the sunspot by enhanced hydromagnetic wave radiation. Both processes would reduce the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/44343
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  • 2
    Electronic Resource
    Electronic Resource
    Resolution of the Hα double-limb controversy (1968)
    Springer
    Solar physics 3 (1968), S. 269-281 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The discussion of the Hα double limb had reached the point where the question of its existence as a real solar phenomenon could not be resolved without new observations made with the Lockheed filter and the Mount Wilson spectroheliograph. A study of the instrumental profiles had indicated that there was sufficient off-band light to produce the observed inner limb step in the Mount Wilson instrument, but this analysis was not completely satisfactory because of limitations inherent in the measurement of instrument functions with a Hg-198 source. The instrumental profile work did indicate, however, that the spectral purity of the instruments in question could be substantially improved by the use of narrow-band interference filters. An experimental program was thus launched to determine the effect of such a blocking filter on the appearance of the Hα limb. The results of these observations with three Halle filter systems and the Mount Wilson spectroheliograph are that the inner limb completely disappears at the center of Hα when a blocking filter is used to reduce unwanted light, which originates at wavelengths beyond ±0.8 Å. In addition, the contrast and visibility of the chromospheric fine structure is increased by eliminating the off-band light. Thus the experiment conclusively demonstrates that the apparent inner limb is not a solar feature but is due entirely to instrumental parasitic light.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155162
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    A measurement of the solar H and K profiles (1968)
    Springer
    Solar physics 3 (1968), S. 523-530 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new series of photometric observations of the H and K lines were obtained at Sacramento Peak Observatory in 1964 and 1965. In both the observations and the data reduction special attention was given to obtaining a suitable average over the solar fine structure and to defining a proper reference continuum. The results are that the central intensities of H and K are the same and equal to 4.2% of the continuum. The limb-darkening curves at the line centres are also the same for both lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151934
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Analysis of the 5 min oscillatory photospheric motion (1973)
    Springer
    Solar physics 31 (1973), S. 23-53 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Four Mt. Wilson measurements (T〉4 h) of the photospheric motion at one point on the Sun are shown to have the characteristics of a narrow-band random process. The motion is shown to have a characteristic correlation time of 23 min and a mean power spectrum that is a smooth, single-peaked function centered at 3.4 mHz. In order to make this classification we use the analytic signal to estimate the amplitude, phase, and frequency as functions of time. The power spectrum analysis differs from the common approaches in that it uses the theoretical expression for the mean spectrum for a sequence of random pulses. Because of the random nature of the motion, we doubt the existence of more than one eigenfrequency characteristic of the photosphere as a whole. Likewise, any description of the observed motion in terms of simple deterministic functions will be inadequate for the data used here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156071
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  • 5
    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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  • 6
    Electronic Resource
    Electronic Resource
    Initial CHIP He I Observations of Solar Limb Activity (1998)
    Springer
    Solar physics 182 (1998), S. 97-105 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A new instrument capable of 3-min time resolution full-disk and limb observations in the Hei 1083 nm spectral line has been in operation at the High Altitude Observatory's Mauna Loa Solar Observatory (MLSO) since April 1996. We discuss instrument capabilities and performance and present some initial observations of limb activity from the first year of instrument operation. We compare limb Hei and Hα observations of quiescent and active prominences, comment on the role of Doppler shifts in interpreting the Hei observations, and illustrate the use of disk/limb Hei observations of a CME-associated eruptive filament in mass-ejection studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005010304281
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    Paper (German National Licenses)
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  • 7
    Electronic Resource
    Electronic Resource
    Measurements of the limb darkening in the forbidden Mgi line at 4571.1 Å (1972)
    Springer
    Solar physics 23 (1972), S. 18-25 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report high resolution measurements of the center-to-limb variation of the Mgi line at 4571.1 Å. This forbidden line is of interest because it should be formed in LTE. Comparison of our measurements with the Harvard-Smithsonian Reference Atmosphere show that the line center radiation originates in the temperature minimum region from 330 to 550 km above the point where τ continuum = 1. Observations near the limb confirm that the temperature minimum is ∼4200K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153888
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  • 8
    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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  • 9
    Electronic Resource
    Electronic Resource
    The spectra of near-vertical structures on the solar disk (1972)
    Springer
    Solar physics 27 (1972), S. 27-33 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Bright emission arches in the spectra of Hα and the Ca II (H and K lines) are identified as the spectroscopic picture of the chromospheric network as it appears near the solar limb. Analysis of the geometrical properties of these spectroscopic arches indicates that the average network is a diverging sheet with a divergence angle of ∼ 50°. This sheet extends to 2600 km and 2000 km as an opaque emission feature in Hα and the Ca II (H and K) lines, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151766
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    Paper (German National Licenses)
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  • 10
    Electronic Resource
    Electronic Resource
    Temporal variations of the magnetic field in sunspots (1974)
    Springer
    Solar physics 35 (1974), S. 309-316 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We obtained simultaneous spectra with a spatial resolution of 1/2″ and a temporal resolution of 15 s in Hα, Ca ii-K, Caii 8542 Å, and three Fei lines of the sunspot group responsible for the large flares of August, 1972 (McMath No. 11976). A time series taken 1972, August 3 in the Fei 6173 Å Zeeman sensitive line was analyzed for oscillations of field strength and the angle between the field and the line of sight, and for changes of the field associated with the Ca ii-K umbral flashes discovered by Beckers and Tallant (1969). The power spectra show no significant peaks, conflicting with the results of Mogilevskii et al. (1972) who reported oscillations in the longitudinal component of the field strength with periods of 56, 90, and 150 s. Changes in the field were not observed to be correlated with the occurrence of umbral flashes. These results place restrictions on magnetic modes of energy transport between the photospheric layers and the chromospheric layers where the umbral flashes are observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151951
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    Paper (German National Licenses)
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