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  • 1
    Electronic Resource
    Electronic Resource
    Image-Tube Systems (1973)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Astronomy and Astrophysics 11 (1973), S. 95-114 
    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.11.090173.000523
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic fields, convection and solar luminosity variability (1982)
    [s.l.] : Nature Publishing Group
    Nature 297 (1982), S. 208-209 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The convective process is plainly manifest at the Sun's surface by the granulation pattern. Rising bright granules, transporting excess energy which is then radiated into space, are surrounded by the cooler intergranule gas which is falling. This causes a velocity-brightness correlation which in ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/297208a0
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  • 3
    Electronic Resource
    Electronic Resource
    Motions in solar magnetic tubes (1978)
    Springer
    Solar physics 58 (1978), S. 347-361 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The line-centre magnetogram technique has been used to study velocities at spatial scales ≃5″ in several umbras without interference from light scattered from the surrounding non-magnetic photosphere. In addition, more traditional velocity observations of one sunspot were also analysed. The velocities are highly variable within any spot and from one spot to another. Rms velocities in Hα, b1, 5233 and 5166 Å were typically ±0.6, ±0.20, ±0.10, and ±0.17 km s−1 during present observations, but factors of 2 smaller or larger are not uncommon. In 5166 and 5233 Å these velocities are about two-thirds of those in non-magnetic photospheric regions. In Hα there are umbral intensity variations whose maxima at Δλ = ±0.39 Å occur simultaneously with downward velocity maxima measured at the same Δλ. Intensity maxima at line centre lag by 12 s, demonstrating that there are waves propagating upwards. The corresponding height difference, 60– 70 km at the velocity of sound, requires excitation of Hα at much higher levels in the umbral atmosphere than if in LTE. For about one-quarter of the observations it is possible to match the Hα and 5233 Å waveforms; velocities in the latter lead those in Hα by 27 s on average, also indicating outward wave propagation and, at the velocity of sound, a difference in the mean heights of formation of about 150 km. There is no significant phase difference between the 5166 Å and b1 lines. The velocity spectrum is variable in all lines, but in general has maxima at shorter periods in Hα (∽200 s) than at lower levels. The estimated outward wave flux for the spatial scales studied is ≪3 × 106 erg cm−2 s−1 at the 5233 Å level, much lower than previous estimates and far too low to produce any significant cooling. This conclusion is believed valid for all periods above about 7 s.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157281
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  • 4
    Electronic Resource
    Electronic Resource
    Solar rotation, 1966–68 (1969)
    Springer
    Solar physics 7 (1969), S. 144-146 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148410
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  • 5
    Electronic Resource
    Electronic Resource
    Cooling of the Sun's photosphere coincident with increased sunspot activity (1978)
    [s.l.] : Nature Publishing Group
    Nature 272 (1978), S. 340-341 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The strengths of selected Fraunhofer lines depend critically on temperature, as indicated by the Saha-Boltzman formula. For thermal monitoring, a 3 A spectral interval at 5,380 A is observed using a double-pass high dispersion scanning spectrometer1. Within this interval are three lines having ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/272340a0
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  • 6
    Electronic Resource
    Electronic Resource
    Observations of sunspot umbral velocity oscillations (1972)
    Springer
    Solar physics 27 (1972), S. 80-88 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Sunspot umbral molecular lines have been used to look for the oscillatory velocities in the umbra. Power spectrum analysis showed conspicuous power for periods in the range between 448 and 310 s. The maximum peak-to-peak amplitude of the umbral oscillatory velocity component is observed to be in the order of 0.5 km s−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151772
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  • 7
    Electronic Resource
    Electronic Resource
    Spatio-temporal fluctuations in HeI 10830 Å line parameters: Evidence for spicule formation (1992)
    Springer
    Solar physics 138 (1992), S. 107-121 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The equivalent width, line depth, line width, and Doppler shift of the He i 10830 Å line were extracted from two time series of spectra. Scatter plots of time-averaged line depth, line width, and Doppler shifts, as well as the root mean square temporal fluctuation of these quantities against the time-averaged equivalent width at a few hundred spatial locations were obtained. The statistical behaviour of these line parameters and their fluctuations was used to infer plausible reasons for the fluctuations. Examination of these results showed that the line parameter fluctuations could be caused by fluctuations in the coronal UV radiation (which could drive the spicules) or by the appearance of density inhomogeneities such as spicules within the line forming domain. In either case, the data can be interpreted as representing the initial phases of spicules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146199
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  • 8
    Electronic Resource
    Electronic Resource
    Sun as a star: Rotation rates from the Ca K-index (1987)
    Springer
    Solar physics 109 (1987), S. 387-391 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Daily measurements for 18 months made at Tucson of the Ca K-index in integrated sunlight have been used to derive solar rotation rates. Power spectral analysis shows that one can obtain a well defined value of solar rotation rate in a period of six months, provided the data are fairly continuous. One might suppose it is possible to study the variation of solar (or stellar) rotation rate with time, a variation arising from a combination of differential rotation and shifts in the active latitude. A comparison between our observed rates and the prevailing dominant activity zones does not support this supposition, at least for the interval studied. Rather, our rates seem to depend on the circumstances of sampling and active region birth and decay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00160661
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  • 9
    Electronic Resource
    Electronic Resource
    Spectral analysis and the two-dimensional distribution of physical parameters in a quiescent prominence (1987)
    Springer
    Solar physics 114 (1987), S. 245-252 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The profiles of Hα and Ca ii K lines of a arch quiescent prominence on April 1, 1971 have been analyzed and the two-dimensional distributions of electron temperature T e , micro-turbulence velocity v t and the column number density of hydrogen along the line-of-sight N H have been obtained. T e , υ t , and N H are found to be 7500 K, 6 km s−1 and 2.2 × 1018 cm−2 on an average, respectively. The electron temperature at the central part of the prominence and along the two arcades are greater than that at the edges, while the distribution of the micro-turbulence velocity in these regions is opposite. There is no systematic variation in T e and v t , from the center to the periphery as described by Hirayama (1971). The column number density in the central region is lower than that at the two edges. The contour lines of T e , υ t , and N H are predominantly vertical rather than horizontal. This implies that the height-variation of physical parameters in filamentary structure is small. The arrangement of this structure in the prominence is likely to be arched and is probably in the direction of magnetic field lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00167344
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  • 10
    Electronic Resource
    Electronic Resource
    Ca ii K2V spectral features and their relation to small-scale photospheric magnetic fields (1982)
    Springer
    Solar physics 80 (1982), S. 227-231 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Although the Ca ii K232 network is known to be cospatial with magnetic elements there has been doubt as to the magnetic origin of the fainter K2V points. We demonstrate that weak magnetic elements also lie at the roots of the K2V points, and because the latter are numerous they may contribute sensibly to the integrated light profile of Ca ii K.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147970
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