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  • 1
    Electronic Resource
    Electronic Resource
    Coronal holes and solar magnetic fields (1979)
    Springer
    Space science reviews 23 (1979), S. 139-158 
    Details
    ISSN: 1572-9672
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Since 1972, nearly continuous observations of coronal holes and their associated photospheric magnetic fields have been made using a variety of satellite and ground-based equipment. The results of comparisons of these observations are reviewed and it is demonstrated that the structure and evolution of coronal holes is basically governed by the large-scale distribution of photospheric magnetic flux. Non-polar holes form in the decaying remnants of bipolar magnetic regions in areas with a large-scale flux imbalance. There is strong indirect evidence that the magnetic field in coronal holes is always open to interplanetary space but not all open-field regions have associated coronal holes. The well-observed declining phase of the last solar cycle was characterized by stable magnetic field and coronal hole patterns which were associated with recurrent, high-speed wind streams and interplanetary magnetic field patterns at the Earth. The ascending phase of the current cycle has been characterized by transient magnetic field and coronal hole patterns which tend to occur at high solar latitudes. This shift in magnetic field and coronal hole patterns has resulted in a less obvious and more complicated association with high-speed wind streams at the Earth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00173808
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  • 2
    Electronic Resource
    Electronic Resource
    Simulations of the sun's polar magnetic fields during sunspot cycle 21 (1987)
    Springer
    Solar physics 108 (1987), S. 47-59 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Regarding new bipolar magnetic regions as sources of flux, we have simulated the evolution of the radial component of the solar photospheric magnetic field during 1976–1984 and derived the corresponding evolution of the line-of-sight polar fields as seen from Earth. The observed timing and strength of the polar-field reversal during cycle 21 can be accounted for by supergranular diffusion alone, for a diffusion coefficient of 800 km2 s-1. For an assumed 300 km2 s-1 rate of diffusion, on the other hand, a poleward meridional flow with a moderately broad profile and a peak speed of 10 m s-1 reached at about 5° latitude is required to obtain agreement between the simulated and observed fields. Such a flow accelerates the transport of following-polarity flux to the polar caps, but also inhibits the diffusion of leading-polarity flux across the equator. For flows faster than about 10 m s-1 the latter effect dominates, and the simulated polar fields reverse increasingly later and more weakly than the observed fields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00152076
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  • 3
    Electronic Resource
    Electronic Resource
    Giant solar arches and coronal mass ejections in November 1980 (1989)
    Springer
    Solar physics 122 (1989), S. 131-143 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Using data from the SOLWIND coronagraph and photometers aboard HELIOS-A we examine coronal mass ejections from an active region which produced a series of giant post-flare coronal arches. HXIS X-ray observations reveal that in several cases underlying flares did not disrupt these arch structures, but simply revived them, enhancing their temperature, density and brightness. Thus we are curious to know how these quasi-stationary X-ray structures could survive in the corona in spite of recurrent appearances of powerful dynamic flares below them. We have found reliable evidence that two dynamic flares which clearly revived the preexisting giant arch were not associated with any mass ejection. After two other flares, which were associated with mass ejections, the arch might have been newly formed when the ejection was over. In one of these cases, however, the arch had typical characteristics of a revived structure so that it is likely that it survived a powerful mass ejection nearby. In a magnetic configuration of the arch which results from potential-field modelling (Figure 1(b)) such a survival seems possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00162831
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  • 4
    Electronic Resource
    Electronic Resource
    The decay of the mean solar magnetic field (1986)
    Springer
    Solar physics 103 (1986), S. 203-224 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have analyzed the effects that differential rotation and a hypothetical meridional flow would have on the evolution of the Sun's mean line-of-sight magnetic field as seen from Earth. By winding the large-scale field into strips of alternating positive and negative polarity, differential rotation causes the mean-field amplitude to decay and the mean-field rotation period to acquire the value corresponding to the latitude of the surviving unwound magnetic flux. For a latitudinally broad two-sector initial field such as a horizontal dipole, the decay is rapid for about 5 rotations and slow with a t −1/2 dependence thereafter. If a poleward meridional flow is present, it will accelerate the decay by carrying the residual flux to high latitudes where the line-of-sight components are small. The resulting decay is exponential with an e-folding time of 0.75 yr (10 rotations) for an assumed 15 m s−1 peak meridional flow speed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147824
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  • 5
    Electronic Resource
    Electronic Resource
    Simulations of the gross solar magnetic field during sunspot cycle 21 (1986)
    Springer
    Solar physics 106 (1986), S. 251-268 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Regarding new bipolar magnetic regions as sources of flux, we have simulated the evolution of the radial component of the solar photospheric magnetic field during 1976–1984 with a spatial resolution of about 34 000 km, and have derived the corresponding evolution of its absolute value averaged over the visible disk. For nominal values of the transport parameters, this simulated gross field is in close, though imperfect, agreement with the observed gross field and its associated indices of solar activity. By analyzing the response of the simulated gross field to variations in the transport parameters and the source properties, we find that the simulated field originates in newly erupted bipolar regions. The lifetimes of these regions are almost always less than 3 mo. Consequently, the strength of the simulated gross field is a measure of the current level of solar activity, and any recurrent patterns with lifetimes in excess of 6 mo must reflect the continuing eruption of new flux at ‘active longitudes’ rather than the persistence of old flux in long-lived magnetic structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00158496
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  • 6
    Electronic Resource
    Electronic Resource
    The origin of the 28- to 29-day recurrent patterns of the solar magnetic field (1986)
    Springer
    Solar physics 104 (1986), S. 425-429 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Numerical simulations of the Sun's mean line-of-sight magnetic field suggest an origin for the 28-to 29-day recurrent patterns of the field and its associated interplanetary phenomena. The patterns are caused by longitudinal fluctuations in the eruption of new magnetic flux, the transport of this flux to mid latitudes by supergranular diffusion and meridional flow, and the slow rotation of the resulting flux distributions at the 28- to 29-day periods characteristic of those latitudes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00159092
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  • 7
    Electronic Resource
    Electronic Resource
    Coronal mass ejection associated with the stationary post-flare arch of 21–22 May 1980 (1986)
    Springer
    Solar physics 103 (1986), S. 399-408 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract By using a combination of X-ray (HXIS), Hα (Haleakala), white-light corona (Solwind), and zodiacal light (Helios) images on 21–22 May, 1980 we demonstrate, and try to explain, the co-existence of a coronal mass ejection with a stationary post-flare coronal arch. The mass ejection was seen, both by Solwind and Helios, in prolongation of the path of a powerful spray, whereas the active region filament did not erupt. A tentative comparison is made with other occurrences of stationary, or quasi-stationary post-flare coronal arches.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147838
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  • 8
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    Simulations of the sun's polar magnetic fields during sunspot cycle 21 (1987)
    Springer
    Details
    Publication Date: 1987-03-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 9
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    Simulations of the gross solar magnetic field during sunspot cycle 21 (1986)
    Springer
    Details
    Publication Date: 1986-08-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 10
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    Giant solar arches and coronal mass ejections in November 1980 (1989)
    Springer
    Details
    Publication Date: 1989-03-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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