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  • 1980-1984  (3)
  • 1975-1979  (1)
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  • 1
    Electronic Resource
    Electronic Resource
    Profiles of Hi (La), Mgii (h and k), Caii (H and K) Lines of an active filament at the limb, with the LPSP instrument aboard the OSO-8 Satellite (1979)
    Springer
    Solar physics 61 (1979), S. 39-59 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We scanned the H i Lα, Mg ii h and k, Ca ii K and H lines simultaneously with the LPSP instrument on OSO-8, to investigate the low and moderate temperature regions of an ‘active region filament’. The Lα line is not reversed except for the innermost position in the prominence. Intensity (k/h), (K/H) ratios are respectively 2 and 1.1, indicating that the Mg ii lines are optically thin, and that Ca ii K is saturated, although not clearly reversed. The results obtained during the second sequence of observations (K saturated before Lα for example) indicate that within the size of the slit (1″ × 10″) we are not observing the same emitting features in the different lines. We also observe an important line-of-sight velocity at the outer edge of the feature, increasing outwards from a few km s−1 to 20 km s−1 within 2″. Less than half an hour later, this velocity is reduced to 15 km s−1 while the intensities increase. Full width at half maximum intensities for this component indicate turbulence variations from 22 to 30 km s−1. The observed high velocities at the top of the prominence can be compared with radial velocities that Mein (1977) observed in Hα at the edges of an active filament and interpreted as velocity loops slightly inclined on the axis of the filament.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00155445
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    OSO-8 observations of CaII H and K, MgII h and k, Lα and Lβ above a sunspot (1981)
    Springer
    Solar physics 69 (1981), S. 289-300 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Observations with the French (L.P.S.P.) experiment on board OSO-8 of a sunspot and nearby plage region are described. The behaviour of the emission cores of the Ca II H and K and Mg II h and k resonance lines is very similar and the correspondence in intensity between the four lines persists in all observed features. In contrast, the Lyman lines show little correlation with the other lines. Their emission regions appear broader in the spectroheliograms than the underlying sunspot structure and must not necessarily possess a counterpart in lower layers. From the central intensity of Lα above the umbra an electron density of 4.3 × 1010 cm-3 ≲n e * ≲2.3 × 1011 cm-3 at 20 000 K is estimated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149995
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Structure and physics of solar faculae (1982)
    Springer
    Solar physics 78 (1982), S. 83-100 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The OSO-8 satellite enabled us to study various characteristics of the profiles of Si ii, Si iv, C iv, and O vi lines above active areas of the Sun, as well as above quiet areas, and to derive some physical properties of the transition region between chromosphere and corona (CCT): (i) The study of the lines shows a general tendency for the microvelocity fields on the average to be nearly constant for the heights corresponding to T 〉 105 K; however they seem to slightly increase with height in quiet areas, and decrease in active areas. (ii) A multicomponent model of the CCT is however quite necessary, and its geometry is far from being a set of plane-parallel columns. It is similar to an association of moving knots within the non-moving principal component of the matter. (iii) The proportion of mass, in the knots relative to that in the non-moving component, is several times larger in active regions than in quiet regions. (iv) In the knots, the non-thermal microvelocity fields are smaller in active regions and seem to decrease for T increasing above 105 K, contrary to what happens in the steady principal component. Of course, we consider that microturbulence and Doppler shift are two aspects of the same distribution of velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151145
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    O VI (λ = 1032 Å) profiles in and above an active region prominence, compared to quiet Sun center and limb profiles (1980)
    Springer
    Solar physics 68 (1980), S. 187-206 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract O vi (λ = 1032 Å) profiles have been measured in and above a filament at the limb, previously analyzed in H i, Mg ii, Ca ii resonance lines (Vial et al., 1979). They are compared to profiles measured at the quiet Sun center and at the quiet Sun limb. Absolute intensities are found to be about 1.55 times larger than above the quiet limb at the same height (3″); at the top of the prominence (15″ above the limb) one finds a maximum blue shift and a minimum line width. The inferred non-thermal velocity (29 km s−1) is about the same as in cooler lines while the approaching line-of-sight velocity (8 km s−1) is lower than in Ca ii lines. The O vi profile recorded 30″ above the limb outside the filament is wider (FWHM = 0.33 Å). It can be interpreted as a coronal emission of O vi ions with a temperature of about 106 K, and a non-thermal velocity (NTV) of 49 km s−1. This NTV is twice the NTV of quiet Sun center O vi profiles. Lower NTV require higher temperatures and densities (as suggested by K-coronameter measurements). Computed emission measures for this high temperature regime agree with determinations from disk intensities of euv lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00153276
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    Paper (German National Licenses)
    Fulltext
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