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  • 1975-1979  (8)
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  • 1
    Electronic Resource
    Electronic Resource
    On the occurrence of sympathetic flares (1976)
    Springer
    Solar physics 48 (1976), S. 275-286 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have tried to determine whether statistical evidence on the occurrence of sympathetic flares, which is negative for whole-disk data, can be found for particular, physically connected, pairs of active regions. Recently, Simnett (1974) and Gergely and Erickson (1975) claimed to have found such evidence, but their results were based on incorrect computations of the random incidence of flares. If the correct formula is applied, the supposed evidence disappears. The results are negative also for pairs of active regions interconnected with magnetic loops visible in soft X-rays during the Skylab mission. The only positive result (with statistical confidence of 3.4 σ) is found for pairs of active regions, which are closer than 30° to each other, without specifying any kind of physical relationship. For such pairs of regions the occurrence of short-time (〈 20 min) intervals between flares is increased, but the time interval pattern does not correspond to any mode of propagation of a triggering agent in the solar atmosphere. Therefore, if the increase has real physical significance, it would be indicative of some kind of subphotospheric synchronization of activity in nearby ‘sympathetic’ active regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151996
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Transequatorial loops interconnecting McMath regions 12472 and 12474 (1977)
    Springer
    Solar physics 52 (1977), S. 69-90 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We discuss the life-story of a transequatorial loop system which interconnected the newly born active region McMath 12474 with the old region 12472. The loop system was probably born through reconnection accomplished 1.5 to 5 days after the birth of 12474 and the loops were observed in soft X-rays for at least 1.5 days. Transient ‘sharpenings’ of the interconnection and a striking brightening of the whole loop system for about 6 hr appear to be caused by magnetic field variations in the region 12474. A flare might have been related to the brightening, but only in an indirect way: the same emerging flux could have triggered the flare and at the same time strengthened the magnetic field at the foot-points of the loops. Electron temperature in the loop system, equal to 2.1 × 106 K in its quiet phase, increased to 3.1 × 106 K during the brightening. Electron density in the loop system was ≤ 1.3 × 109 cm−3 and it could be estimated to ∼7 × 108 cm−3 prior to the brightening. During the brightening the loops became twisted. There was no obvious effect whatsoever of the activity in 12474 upon the in erconnected old region. The final decay of the loop system reflected the decay of magnetic field in the region 12474.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00935791
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    Paper (German National Licenses)
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  • 3
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    On the occurrence of sympathetic flares (1976)
    Springer
    Details
    Publication Date: 1976-06-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 4
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    Transequatorial loops interconnecting McMath regions 12472 and 12474 (1977)
    Springer
    Details
    Publication Date: 1977-04-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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    PAPER CURRENT
  • 5
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    Transequatorial loops interconnecting McMath regions 12472 and 12474 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper reviews the life history of one transequatorial loop in a system observed in soft X-rays for at least 1.5 days and which interconnected a newly born active region with an old region. The birth of the selected loop is discussed along with properties of the interconnected active regions, sharpening and brightening of the loop, decay of the loop system, and physical relations between the interconnected regions. It is concluded that: (1) the loop was most probably born via reconnection of magnetic-field lines extending from the two active regions toward the equator, which occurred later than 33 hr after the younger region was born; (2) the fully developed interconnection was composed of several loops, all of which appeared to be rooted in a spotless magnetic hill of preceding northern polarity but were spread over two separate spotty regions of southern polarity in the magnetically complex new region; (3) the loop electron temperature increased from 2.1 million to 3.1 million K in one to three hours when the loop system brightened; and (4) the loops became twisted during the brightening, possibly due to their rise in the corona while remaining rooted in moving magnetic features in the younger region.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 52; Apr. 197
    Format: text
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  • 6
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    Quest for ultrahigh resolution in X-ray optics (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A program of solar X-ray astronomy using grazing incidence optics has culminated in X-ray images of the corona having one arc second spatial resolution. These images have demonstrated that, in general, X-ray optics can be fabricated to their specifications and can provide the level of resolution for which they are designed. Several aspects of these programs relating to the performance of X-ray optics in regard to resolution, including the point response function, the variation of resolution with off-axis position and the recognition that nearly all solar X-ray images have been film limited, are discussed. By extending the experience gained on this and other programs it is clearly possible to design and fabricate X-ray optics with sub arc sec resolution. The performance required to meet the scientific objectives for the remainder of the century are discussed in relation to AXIO, an Advanced X-Ray Imaging Observatory for solar observations which is proposed for flight on the Space Shuttle. Several configurations of AXIO are described, each of which would be a major step in the quest for ultrahigh-resolution observations.
    Keywords: ASTRONOMY
    Type: Space optics: Imaging X-ray optics workshop; May 22, 1979 - May 24, 1979; Huntsville, AL
    Format: text
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    NASA TECHNICAL REPORTS
  • 7
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    On the occurrence of sympathetic flares (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Random-coincidence formulas are applied to the data used in previous studies of alleged sympathetic flares to determine whether statistical evidence on the occurrence of such flares can be found for specific physically connected pairs of active regions. Only those active regions that are interconnected by magnetic loops in soft X-rays on Skylab photographs are considered to be physically connected. All pairs of flaring active regions (both interconnected and otherwise) observed on the sun during the Skylab flight are also evaluated. The only positive result is obtained with statistical confidence of 3.4 sigmas for pairs of active regions separated by no more than 30 deg. The occurrence of short time intervals between flares is shown to be increased for such active-region pairs, but the pattern of time intervals is found not to correspond with any propagation mode of a triggering agent in the solar atmosphere. It is suggested that some subphotospheric synchronization of activity in nearby plages and sunspot groups could increase the number of short time intervals between flares at different locations without any actual influence of one 'sympathetic' flare upon another, leading to the concept of 'sympathetic active regions' instead of 'sympathetic flares'.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 48; June 197
    Format: text
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  • 8
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    Skylab observations of X-ray loops connecting separate active regions (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: One hundred loops interconnecting 94 separate active solar regions detectable in soft X-rays were identified during the Skylab mission. While close active regions are commonly interconnected with loops, the number of such interconnections decreases steeply for longer distances; the longest interconnecting loop observed in the Skylab data connected regions separated by 37 deg. Several arguments are presented which support the point of view that this is the actual limit of the size of magnetic interconnections between active regions. No sympathetic flares could be found in the interconnected regions. These results cast doubt on the hypothesis that accelerated particles can be guided in interconnecting loops from one active region to another over distances of 100 deg or more and eventually produce sympathetic flares in them.
    Keywords: SOLAR PHYSICS
    Type: Symposium and Workshop on Results from Coordinated Upper Atmosphere Measurement Programs; May 29, 1975 - May 31, 1975|Open Meetings of Working Groups on Physical Sciences; May 29, 1975 - Jun 07, 1975; Varna; Bulgaria
    Format: text
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