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  • 1
    Electronic Resource
    Electronic Resource
    Why measure astrophysical X-ray spectra? (1977)
    [s.l.] : Nature Publishing Group
    Nature 267 (1977), S. 410-411 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The main thrust of their argument is to point out the ill-conditioning of the equations that require to be inverted in order to carry out an analysis based on emission measures, and to illustrate this by reference to a 1970 publication by Batstone et al.2, an early attempt to do this in the X-ray ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/267410a0
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  • 2
    Electronic Resource
    Electronic Resource
    Identification of the Solar Spectrum in the Region 60–170 Å (1965)
    [s.l.] : Nature Publishing Group
    Nature 206 (1965), S. 808-809 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Below 170 Å, photography of the solar spectrum presents certain difficulties due to absorption of radiation by the aluminium foil filter commonly used to reduce fogging due to scatter of visible light. This problem is solved when photoelectric detectors, insensitive to visible light, are ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/206808a0
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  • 3
    Electronic Resource
    Electronic Resource
    Classification of Iron Lines in the Spectrum of the Sun and Zeta in the Range 167 Å to 220 Å (1965)
    [s.l.] : Nature Publishing Group
    Nature 206 (1965), S. 390-392 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] At Culham, new experimental results, recently obtained, have led to the classification of many of the more intense lines in this group. It is the purpose of this communication to give a preliminary account of this work. A paper in course of preparation will detail the reasons leading to these ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/206390a0
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  • 4
    Electronic Resource
    Electronic Resource
    Preface (1972)
    Springer
    Space science reviews 13 (1972), S. iii 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213473
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  • 5
    Electronic Resource
    Electronic Resource
    Dielectronic satellite spectra in the soft X-ray region (1972)
    Springer
    Space science reviews 13 (1972), S. 655-664 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Satellite lines, situated on the long wavelength side of the helium-like ion resonance line, can be observed in highly-ionized ions both in laboratory sources and from the Sun. Although seen for more than 30 years, these lines have only recently been classified in detail as inner-shell transitions in lithium-like ions. Laboratory experiments have shown that under steady-state conditions these satellites are produced by dielectronic recombination, although in transient ionizing plasmas direct inner-shell excitation can be important. Detailed calculations have been carried out for high Z ions up to copper, and the results can be compared with solar flare spectra in iron. Such comparisons allow both the electron temperature and the transient state of the plasma to be determined. Laboratory spectra from such high-Z ions are different in appearance, and may be dominated by processes resulting from the transient ionizing state of the plasma.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00213500
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  • 6
    Electronic Resource
    Electronic Resource
    First Results on it p Modes from GOLF Experiment (1997)
    Springer
    Solar physics 175 (1997), S. 227-246 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The GOLF experiment on the SOHO mission aims to study the internal structure of the Sun by measuring the spectrum of global oscillations in the frequency range 10-7 to 10-2 Hz. Here we present the results of the analysis of the first 8 months of data. Special emphasis is put into the frequency determination of the p modes, as well as the splitting in the multiplets due to rotation. For both, we show that the improvement in S/N level with respect to the ground-based networks and other experiments is essential in achieving a very low-degree frequency table with small errors ∼ 2 parts in 10-5). On the other hand, the splitting found seems to favour a solar core which does not rotate slower than its surface. The line widths do agree with theoretical expectations and other observations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004942929956
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  • 7
    Electronic Resource
    Electronic Resource
    Eit Observations of the Extreme Ultraviolet Sun (1997)
    Springer
    Solar physics 175 (1997), S. 571-599 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The Extreme Ultraviolet Imaging Telescope (EIT) on board the SOHO spacecraft has been operational since 2 January 1996. EIT observes the Sun over a 45 x 45 arc min field of view in four emission line groups: Feix, x, Fexii, Fexv, and Heii. A post-launch determination of the instrument flatfield, the instrument scattering function, and the instrument aging were necessary for the reduction and analysis of the data. The observed structures and their evolution in each of the four EUV bandpasses are characteristic of the peak emission temperature of the line(s) chosen for that bandpass. Reports on the initial results of a variety of analysis projects demonstrate the range of investigations now underway: EIT provides new observations of the corona in the temperature range of 1 to 2 MK. Temperature studies of the large-scale coronal features extend previous coronagraph work with low-noise temperature maps. Temperatures of radial, extended, plume-like structures in both the polar coronal hole and in a low latitude decaying active region were found to be cooler than the surrounding material. Active region loops were investigated in detail and found to be isothermal for the low loops but hottest at the loop tops for the large loops. Variability of solar EUV structures, as observed in the EIT time sequences, is pervasive and leads to a re-evaluation of the meaning of the term ‘quiet Sun’. Intensity fluctuations in a high cadence sequence of coronal and chromospheric images correspond to a Kolmogorov turbulence spectrum. This can be interpreted in terms of a mixed stochastic or periodic driving of the transition region and the base of the corona. No signature of the photospheric and chromospheric waves is found in spatially averaged power spectra, indicating that these waves do not propagate to the upper atmosphere or are channeled through narrow local magnetic structures covering a small fraction of the solar surface. Polar coronal hole observing campaigns have identified an outflow process with the discovery of transient Fexii jets. Coronal mass ejection observing campaigns have identified the beginning of a CME in an Fexii sequence with a near simultaneous filament eruption (seen in absorption), formation of a coronal void and the initiation of a bright outward-moving shell as well as the coronal manifestation of a ‘Moreton wave’.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004902913117
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  • 8
    Electronic Resource
    Electronic Resource
    Eit and LASCO Observations of the Initiation of a Coronal Mass Ejection (1997)
    Springer
    Solar physics 175 (1997), S. 601-612 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We present the first observations of the initiation of a coronal mass ejection (CME) seen on the disk of the Sun. Observations with the EIT experiment on SOHO show that the CME began in a small volume and was initially associated with slow motions of prominence material and a small brightening at one end of the prominence. Shortly afterward, the prominence was accelerated to about 100 km s-1 and was preceded by a bright loop-like structure, which surrounded an emission void, that traveled out into the corona at a velocity of 200–400 km s-1. These three components, the prominence, the dark void, and the bright loops are typical of CMEs when seen at distance in the corona and here are shown to be present at the earliest stages of the CME. The event was later observed to traverse the LASCO coronagraphs fields of view from 1.1 to 30 R⊙. Of particular interest is the fact that this large-scale event, spanning as much as 70 deg in latitude, originated in a volume with dimensions of roughly 35" (2.5 x 104 km). Further, a disturbance that propagated across the disk and a chain of activity near the limb may also be associated with this event as well as a considerable degree of activity near the west limb.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004907307376
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  • 9
    Electronic Resource
    Electronic Resource
    First View of the Solar Core from Golf Acoustic Modes (1997)
    Springer
    Solar physics 175 (1997), S. 247-265 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract After 8 months of nearly continuous measurements the GOLF instrument, aboard SOHO, has detected acoustic mode frequencies of more than 100 modes, extending from 1.4 mHz to 4.9 mHz. In this paper, we compare these results with the best available predictions coming from solar models. To verify the quality of the data, we examine the asymptotic seismic parameters; this confirms the improvements achieved in solar models during the last decade. Using the GOLF set of frequencies for l=0, 1, 2, 3 combined with the LOWL second year data set for l 〉 3 we then carry out inversions to infer properties of the solar core. This largely confirms the previous results down to around 0.1 R⊙, while there remain differences, even closer to the centre, where the present study shows an extreme sensitivity of the inversion results to the values of the frequencies. We finally consider physical processes which may influence directly or indirectly the solar core structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004992727541
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  • 10
    Electronic Resource
    Electronic Resource
    The soft X-ray polychromator for the Solar Maximum Mission (1980)
    Springer
    Solar physics 65 (1980), S. 53-71 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The 1.4–22.4 Å range of the soft X-ray spectrum includes a multitude of emission lines which are important for the diagnosis of plasmas in the 1.5–50 million degree temperature range. In particular, the hydrogen and helium-like ions of all abundant solar elements with Z 〉 7 have their primary transitions in this region and these are especially useful for solar flare and active region studies. The soft X-ray polychromator (XRP) is a high resolution experiment working in this spectral region. The XRP consists of two instruments with a common control, data handling and power system. The bent crystal spectrometer is designed for high time resolution studies in lines of Fe i-Fe xxvi and Ca xix. The flat crystal scanning spectrometer provides for 7 channel polychromatic mapping of flares and active regions in the resonance lines of O viii, Ne ix, Mg xi, Si xiii, S xv, Ca xix, and Fe xxv with 14″ spatial resolution. In its spectral scanning mode it covers essentially the entire 1.4–22.5 Å region. This paper summarizes the scientific objectives of the XRP experiment and describes the characteristics and capabilities of the two instruments. Sufficient technical information for experiment feasibility studies is included and the resources and procedures planned for the use of the XRP within the context of the Solar Maximum Mission is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151384
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