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  • 1
    Electronic Resource
    Electronic Resource
    A possible edge effect in enhanced network (1977)
    Springer
    Solar physics 52 (1977), S. 337-342 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract K-line observations of enhanced network taken with the NASA/SPO Multichannel Spectrometer on 28 September 1975 in support of OSO-8 are discussed. The data show a correlation between core brightness and asymmetry for spatial scans which cross enhanced network boundaries. The implications of this result concerning mass flow in and near supergranule boundaries are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149650
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  • 2
    Electronic Resource
    Electronic Resource
    Magnetic canopies in unipolar regions (1983)
    Springer
    Solar physics 87 (1983), S. 37-42 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Base-height statistics are presented for magnetic canopies in six unipolar magnetic regions which were observed near the limb with the Kitt Peak Vacuum Telescope and Diode Array Magnetograph during the period 25 April–3 July, 1980. As in earlier studies, extensive areas are found to be covered by low-lying canopies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151157
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of fourier phase shifts in the solar Nii 6768 Å line (1989)
    Springer
    Solar physics 120 (1989), S. 211-234 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A formalism is developed to understand better how Doppler shifts of spectrum lines as inferred from phase shifts in the Fourier transforms of line profiles are related to the underlying velocity structures which they are intended to measure. With a standard model atmosphere and a simplified, quasi-LTE treatment of line formation, the formalism is applied to the Nii 6768 Å line which has been selected for use with a network of imaging interferometers under development by the Global Oscillations Network Group (GONG) for research in helioseismology. Fourier phase shifts are found to be a remarkably linear measure of velocity even in the presence of gradients and unresolved lateral variations in the assumed velocity field. An assumed outward increase in amplitude of a model oscillatory velocity is noticeably reflected in the center-to-limb behavior of the simulated velocity measure, and a sample model of solar granulation is found to have a strong influence on the formation of the Fourier phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159876
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  • 4
    Electronic Resource
    Electronic Resource
    The NASA/NSO Spectromagnetograph (1992)
    Springer
    Solar physics 139 (1992), S. 211-232 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The NASA/NSO Spectromagnetograph is a new focal plane instrument for the National Solar Observatory/Kitt Peak Vacuum Telescope which features real-time digital analysis of long-slit spectra formed on a two-dimensional CCD detector. The instrument is placed at an exit port of a Littrow spectrograph and uses an existing modulator of circular polarization. The new instrument replaces the 512-channel Diode Array Magnetograph first used in 1973. Commercial video processing boards are used to digitize the spectral images at video rates and to separate, accumulate, and buffer the spectra in the two polarization states. An attached processor removes fixed-pattern bias and gain from the spectra in cadence with spatial scanning of the image across the entrance slit. The data control computer performs position and width analysis of the line profiles as they are acquired and records line-of-sight magnetic field, Doppler shift, and other computed parameters. The observer controls the instrument through windowed processes on a data control console using a keyboard and mouse. Early observations made with the spectromagnetograph are presented and plans for future development are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159149
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  • 5
    Electronic Resource
    Electronic Resource
    Magnetograph response to canopy-type fields (1982)
    Springer
    Solar physics 79 (1982), S. 247-266 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The response of longitudinal-field magnetographs to magnetic fields which are semi-infinite or confined to a horizontal layer is discussed with respect to the interpretation of solar diffuse fields, observed towards the limb, in terms of magnetic canopy models. Numerical results are presented for several reference solar models and typical ‘calibration’ curves are shown for the C I 9111 Å, Fe I 8688 Å, and Ca II 8542 Å lines in magnetostatic atmospheres derived from a mean model. A procedure is developed for determining the base heights of magnetic canopies from observations with an uncertainty not exceeding the order of a pressure scale height. Until definitive information regarding atmospheric structure inside flux tubes can be developed from theory or observation, reliable field strengths cannot be derived from the data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146243
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  • 6
    Electronic Resource
    Electronic Resource
    The three-dimensional structure of atmospheric magnetic fields in two active regions (1982)
    Springer
    Solar physics 79 (1982), S. 267-278 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The magnetic field above two unrelated active regions on 11 and 12 September, 1974 has been studied using magnetograms obtained in C I 9111, Fe I 8688, Ca II 8542, and Hα. In C I 9111, originating low in the photosphere, the fields are strong and sharply defined. In Ca II 8542 and Hα they are very diffuse, with significant diffuseness also in Fe I 8688, due to the spreading of the field with height to form almost horizontal magnetic canopies over regions free of field at lower levels. Within a region between two small sunspots some 140 Mm apart, the canopy height found is typically 300–400 km. Within a small superpenumbra, the canopy height is ∼ 150–250 km. In extensive areas surrounding the active regions, over one-half the canopy bases are less than 400–500 km above the τ c = 1 level, and over 80% less than 700 km. Arguments are given that the chromospheric fibrils (e.g., in Hα), taken to delineate the field configuration, are not due primarily to lateral variations in field but rather to differences in density or excitation of gas across the lines of force.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146244
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  • 7
    Electronic Resource
    Electronic Resource
    Scaling-law equilibria for calcium in canopy-type models of the solar chromosphere (1982)
    Springer
    Solar physics 79 (1982), S. 279-290 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Scaling laws for resonance line formation are used to obtain approximate excitation and ionization equilibria for a three-level model of singly ionized calcium. The method has been developed for and is applied to the study of magnetograph response in the 8542 Å infrared triplet line to magnetostatic canopies which schematically model diffuse, nearly horizontal fields in the low solar chromosphere. For this application, the method is shown to be efficient and semi-quantitative, and the results indicate the type and range of effects on calcium-line radiation which result from reduced gas pressure inside the magnetic regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146245
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  • 8
    Electronic Resource
    Electronic Resource
    The global oscillation network group site survey (1994)
    Springer
    Solar physics 152 (1994), S. 351-379 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Global Oscillation Network Group (GONG) Project will place a network of instruments around the world to observe solar oscillations as continuously as possible for three years. The Project has now chosen the six network sites based on analysis of survey data from fifteen sites around the world. The chosen sites are: Big Bear Solar Observatory, California; Mauna Loa Solar Observatory, Hawaii; Learmonth Solar Observatory, Australia; Udaipur Solar Observatory, India; Observatorio del Teide, Tenerife; and Cerro Tololo Interamerican Observatory, Chile. Total solar intensity at each site yields information on local cloud cover, extinction coefficient, and transparency fluctuations. In addition, the performance of 192 reasonable components analysis. An accompanying paper describes the analysis methods in detail; here we present the results of both the network and individual site analyses. The selected network has a duty cycle of 93.3%, in good agreement with numerical simulations. The power spectrum of the network observing window shows a first diurnal sidelobe height of 3 × 10−4 with respect to the central component, an improvement of a factor of 1300 over a single site. The background level of the network spectrum is lower by a factor of 50 compared to a single-site spectrum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00680444
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  • 9
    Electronic Resource
    Electronic Resource
    Does Magnetic Flux Submerge at Flux Cancelation Sites? (1999)
    Springer
    Solar physics 190 (1999), S. 35-44 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Simultaneous measurements of the magnetic fields in the photosphere and chromosphere were used to investigate if magnetic flux is submerging at sites between adjacent opposite polarity magnetic network elements in which the flux is observed to decrease or `cancel'. These data were compared with chromospheric and coronal intensity images to establish the timing of the emission structures associated with these magnetic structures as a function of height. We found that most of the cancelation sites show either that the bipole is observed longer in the photosphere than in the chromosphere and corona (44%) or that the timing difference of the disappearance of the bipole between these levels of the atmosphere is unresolved. The magnetic axis lengths of the structures associated with the cancelation sites are on average slightly smaller in the chromosphere than the photosphere. These observations suggest that magnetic flux is retracting below the surface for most, if not all, of the cancelation sites studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005237719407
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  • 10
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    The NASA/NSO Spectromagnetograph (1992)
    Springer
    Details
    Publication Date: 1992-06-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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