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  • 1
    Publication Date: 1985-04-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 2
    Publication Date: 1985-08-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 3
    Publication Date: 1985-01-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 4
    Publication Date: 1985-01-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 5
    Publication Date: 1982-10-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 80 (1982), S. 251-258 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Magnetic field strengths in small umbrae and pores are measured using the line Ti i λ6064.6 Å, which is formed purely in umbrae. We find field strengths between 1900 and 2600 G in the darkest parts of small umbrae and of well established pores; the spread is partly intrinsic. The field strength in diffuse transient ‘protopores’ amounts to 1500 ± 250 G. We demonstrate that usage ofthe well-known magnetic line λ6173.3 Å and other Fe i lines yield systematically smaller magnetic field strengths than Ti i λ6064.6 Å. This is due to blending ofthe σ components with the central component due to photospheric stray light and the π component. Routine measurements are therefore unreliable for small spots 251-01
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 95 (1985), S. 3-14 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe an observing program designed to obtain spectra of sunspots, pores, and other features in active regions using the Vacuum Tower Telescope and Echelle Spectrograph at Sacramento Peak Observatory. The spectral lines used in this study have been especially chosen to allow pointed studies of fine structure in the intensity distribution, and in the velocity and magnetic fields in the photospheric levels of active regions, and to relate this structure to chromospheric observations made in the Caii H line. We demonstrate the capacities of the observing program by two examples: umbral fine structure, and an emerging active region. Although the umbral spectrograms resolve the brightness structure down to less than one arc sec we do not find clear-cut relations in the spatial variations of brightness, magnetic field strength and line-of-sight velocity across the umbral structure. In the emerging active region several processes are observed in their relationship: the rising and draining of an arch-filament system, the convective collapse of flux tubes, and the growth of a sunspot pore by coalescing fluxtubes.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 96 (1985), S. 229-252 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We describe the morphological evolution of photospheric features in an emerging flux region (EFR), on the basis of high-resolution photographs taken with the Vacuum Tower Telescope at Sacramento Peak Observatory. Individual alignments of darkened intergranular lanes have a lifetime of only about 10 min; they may represent the tops of emerging flux loops. Roundish darkened patches within the intergranular lanes (protopores) may precede the birth of a pore, or may disappear again within a few hours. The birth of one pore coincides with the area of a conspicuous downflow observed in the spectrograms. The majority of the pores in the EFR grow in area and darken; their growth times vary between 1 and 6 hr. Various modes of growth are observed. Some pores dissolve again within a few hours after their birth. The long axis of the whole EFR rotates by 2 deg hr-1 towards alignment parallel to the equator, with leading polarity closest to the equator. The ring of pores surrounding the EFR expands with velocities of about 0.7 km s-1 in the east-west direction. There is strong velocity shear: the leading edge of the leading pore moves perpendicular to the general expansion of the ring of pores. Filigree is absent near the fast growing pores of following polarity and near the alignments.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 98 (1985), S. 197-217 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scatter plots of various pairs of spectral-line parameters that describe the magnetic field and the line-of-sight velocity are discussed in order to relate magnetic structures and the line-of-sight velocity field with characteristic areas of an emerging flux region (EFR). Strong magnetic fields, occurring over about 20% of the resolution elements in the EFR, are either slightly to moderately inclined or transverse. Slightly to moderately inclined strong fields occur in patches near the border of the EFR; the filling factors per resolution element are large, and field strengths are between 800 and 2000 G, and up to 2500 G in pores. There are only a few faculae in the EFR; most of these are located near rapidly growing pores of following polarity. The strongly inclined strong magnetic fields, with field strengths exceeding 1000 G, are located in slightly darkened resolution elements near the line B ∥ = 0 separating the magnetic polarities, near large-scale and small-scale upflows. In the central region of the EFR there are some small elements with strongly inclined field of low average field strength of about 500 G, and a tendency for a small-scale upward velocity. These elements may correspond to tops of flux loops during emergence. In 80% of the resolution elements within the EFR the magnetic flux density (averaged over the resolution element) is low, less than 120 G. There is a persistent large-scale velocity field, with upflows near the line B ∥ = 0 separating the magnetic polarities and with downflows near rapidly growing pores of following polarity. Some examples of strong small-scale upflows are found in the central region of the EFR, and strong small-scale downflows near rapidly growing following pores. Within the pores and faculae there are no significant small-scale line-of-sight velocities.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Solar physics 95 (1985), S. 15-36 
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract This paper discusses the analysis of spectrograms of solar magnetic structures obtained with high spatial resolution in both directions of circular polarization, with application to observations of flux emergence. We assume each spatial resolution element to contain two atmospheric components: mean non-magnetic photosphere and unresolved magnetic structure. We first define observable spectral-line parameters, and then calibrate the derivation of magnetic-structure parameters by computer simulations in which we vary the fractional contribution of the magnetic component, its field strength and its field inclination, and the line-of-sight velocity difference between the components. This grid of synthesized profiles then serves to define the uniqueness and margins of trial-and-error fits to the observed parameters. We present results for an emerging flux region. Magnetic flux is present over most of its area. The magnetic field strength outside pores is between 100 and 1700 G, and in one ‘magnetic knot’ it is about 1150 G. The field inclination and the fractional area cannot be determined separately, but the mean magnetic flux density is well determined: it ranges between 80 and 120 G, and in some patches and the knot between 120 and 210 G. There is a strong downflow just outside a fast-growing pore.
    Type of Medium: Electronic Resource
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