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  • 1
    Electronic Resource
    Electronic Resource
    Rotating eruption of an untwisting filament triggered by the 3B flare of 25 April, 1984 (1987)
    Springer
    Solar physics 108 (1987), S. 251-264 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A great 3B flare, whose X-ray class was X13, occurred over a delta-sunspot at 00: 01 UT on April 25, 1984. Before the flare, a strong magnetic shear was found to be formed along the neutral line in the delta-sunspot with shear motions of umbrae. The shear motions of the umbrae were caused by the successive emergence of a magnetic flux rope. Before the flare, several groups of sheared Hα threads and filaments were found to merge into an elongated filament along the neutral line through the delta-sunspot. In the merging process the helical twists were formed in the filament by the reconnection as in the Pneuman's (1983) model. At the post-maximum phase of the flare, the helically twisted filament spouted out with an untwisting rotation. Examining the morphological and dynamical features of the filament eruption, we concluded that it has some typical features of the flare spray and that it seems to be accelerated by the sweeping-magnetictwist mechanism proposed by Shibata and Uchida (1986).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00214165
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  • 2
    Electronic Resource
    Electronic Resource
    The innermost corona observed at the 1973 June 30 eclipse (1986)
    Springer
    Solar physics 106 (1986), S. 95-106 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Slitless flash spectrograms in heights below 8000 km above the solar limb were obtained by the University of Kyoto Expedition at Atar, Mauritania. The integrated intensities of Fexiv λ5303, Fex λ6374, Fexi λ7892, and the continuum are measured as a function of height above the solar limb at eleven points (P.A. = 284–300°) around the third contact point. It is found that a significant amount of the emission in Fex λ6374 originates in chromospheric levels well below 8000 km. This implies that the interspicular region of the chromosphere is occupied by coronal material. The average values of the electron temperature and the electron density in the interspicular region are derived from the Fex λ6374 and the Fexi λ7892 intensities on the assumption of spherical symmetry: T e = 0.9–1.1 × 106 K and N e = 9–10 × 108 cm−3. The intensity variations of the coronal lines and the continuum with position angle are also studied. Strong correlations between Fexiv λ5303 and the continuum and between Fex λ6374 and Fexi λ7892 are found. From the Fex λ6374 intensities it is inferred that there is a density fluctuation in the innermost corona by at least a factor of two.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00161357
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  • 3
    Electronic Resource
    Electronic Resource
    Flares and plasma flow caused by interacting coronal loops (1996)
    Springer
    Solar physics 165 (1996), S. 275-301 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Active region NOAA 7360 was observed in 1992 December with various instruments including the Yohkoh satellite. In this region, a small loop emerged near one of the footpoints of a pre-existing large coronal loop. These loops show evidence that interactions between coronal loops cause flares, microflares, and plasma flow. All of the four flares observed in this region show that brightenings in the small loop occurred first, and then the large loop flared up. The brightenings in the large loop can not occur by themselves, but must be triggered by the brightenings in the small loop. There must be interactions between the loops to cause these flares. As well as the flares, many microflares occurred in the small loop. More than half of them are accompanied by plasma ejection phenomena from the small loop into the large loop. The large loop is filled with ejected plasma with velocities of about 1000 km s−1. These ejection phenomena are considered as X-ray jets. The associated occurrences of the microflares and the jets suggest that they are also caused by interactions between the loops. The recurrent occurrences of the homologous flares and microflares mean that the magnetic field structure in this region inevitably causes the activity due to loop-loop interactions; the flares and jets occur under a common magnetic field structure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00149715
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  • 4
    Electronic Resource
    Electronic Resource
    DOUBLE-LOOP CONFIGURATION OF SOLAR FLARES (1997)
    Springer
    Solar physics 173 (1997), S. 319-346 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We analyzed several flares, which are presumed to be caused by interactions between an emerging loop and an overlying loop. We call such a basic combination of loops a ‘double-loop configuration’, and we reveal its topology on the basis of the microwave and soft X-ray observations of the flares and the magnetograms. In many cases, the magnetic field of the flare loops shows a ‘bipolar + remote unipolar’ structure, rather than a quadrapole structure. The footpoints of two loops are distributed in three magnetic patches, and two of the footpoints of the loops, one from the emerging loop and the other from the overlying loop, are included in a single magnetic polarity patch. Therefore, the two loops form a ‘three-legged’ structure, and the two loops are not anti-parallel as assumed in the traditional reconnection models. Typically, the emergence of a parasitic polarity near the major preceding-polarity region or the following one in an active region creates this configuration, but, in one of the analyzed flares, two active regions are involved in the configuration. Not only the flares, but various other active phenomena – microflares, thermal plasma flows like jets, and surges – occur in the same magnetic configuration. Hence, the interaction between two loops, which forms the three-legged structure, is an important source of the various types of activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004953003558
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  • 5
    Electronic Resource
    Electronic Resource
    Simultaneous multifrequency observations of an eruptive prominence at millimeter wavelengths (1995)
    Springer
    Solar physics 156 (1995), S. 363-375 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Radio images and spectra of an eruptive prominence were obtained from simultaneous multifrequency observations at 36 GHz, 89 GHz, and 110 GHz on May 28, 1991 with the 45-m radio telescope at Nobeyama Radio Observatory (NRO), the National Astronomical Observatory, Japan (NAOJ). The radio spectra indicated that the optical depth is rather thick at 36 GHz whereas it is thin at 89 and 110 GHz. The Hα data, taken at Norikura Solar Observatory, NAOJ, suggest that the eruption of an active region filament was triggered by an Hα flare. The shape and position of the radio prominence generally coincided with those of Hα images. The radio emission is explained with an isothermal cool thread model. A lower limit for the electron temperature of the cool threads is estimated to be 6100 K. The range of the surface filling factors of the cool threads is 0.3–1.0 after the Hα flare, and 0.2–0.5 in the descending phase of the eruptive prominence. The column emission measure and the electron number density are estimated to be of the order of 1028 cm−5 and 1010 cm−3, respectively. The physical parameters of a quiescent prominence are also estimated from the observations. The filling factors of the eruptive prominence are smaller than those of the quiescent prominence, whereas the emission measures and the electron densities are similar. These facts imply that each cool thread of the prominence did not expand after the eruption, while the total volume of the prominence increased.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00670232
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  • 6
    Electronic Resource
    Electronic Resource
    The post flare loops observed at the total eclipse of February 16, 1980 (1986)
    Springer
    Solar physics 105 (1986), S. 133-148 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A post flare loop system was observed on the west limb at the total solar eclipse of February 16, 1980 in Kenya. Analyzing the monochromatic images and the flash spectra, we obtained the following results: (1) the lower part of the post flare loop system is characterized mainly by distinct cool loops of Hα and Fe x 6374. Fe x 6374 emitting plasma (T e = 1.0 × 106 K) is highly concentrated in the loops. The 6374 loops are broader in diameter and located very close to but a little higher than the corresponding Hα loops. The electron densities of the dense part in Hα and Fe x 6374 loops are 1011 cm-3 and 6 × 109cm-3, respectively; (2) the Ca xv emitting region (3.5 × 106 K) is confined to the upper part of the post flare loops. The electron density of this hot region is estimated as 8 × 109 cm-3 from the Ca xv line intensity ratio, I(λ5694)I(λ5445). These observational results led us to construct an empirical model of the post flare loop system which is consistent with the reconnection model of Kopp and Pneuman (1976).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156383
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  • 7
    Electronic Resource
    Electronic Resource
    Mass motions in active region filaments (1989)
    Springer
    Solar physics 124 (1989), S. 227-250 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Mass motions in active region filaments of regions NOAA 4171 and McMath 16208 are analyzed. Both regions were continuously observed with the Zeiss Lyot filter for about a week at the Hida Observatory. As for NOAA 4171, Dopplergrams are made from the Hα filtergrams of 7 wavelengths for the qualitative study of the velocity fields in the filament, and Beckers' cloud model analysis is employed for a quantitative study of them. Dopplergrams of McMath 16208 are also constructed for qualitative analyses to determine whether the results derived from the analysis of NOAA 4171 are applicable to this region. The following results are obtained. Matter in the long-lived filaments, which lie along the magnetic neutral lines, flows generally horizontally and along the axes of the filaments. Since the matter in the filaments is considered to flow along the magnetic field, the magnetic fields in the filaments must be highly sheared. The same patterns of mass flow are found in the same filaments on successive days; some of them last for at least several days. Some filaments show long-lived symmetrical downflows to both of their ends in which the velocity is about 30 km s-1. Such flows are seen both in NOAA 4171 and McMath 16208. We show a morphological model of such flows.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00156268
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  • 8
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    Accurate Measurements of the Brightness of the White-Light Corona at the Total Solar Eclipses on 1 August 2008 and 22 July 2009 (2012)
    Springer
    Details
    Publication Date: 2012-04-19
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 9
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    Rotating eruption of an untwisting filament triggered by the 3B flare of 25 April, 1984 (1987)
    Springer
    Details
    Publication Date: 1987-01-01
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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  • 10
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    Coronal Mass Ejections Observed at the Total Solar Eclipse on 13 November 2012 (2014)
    Springer
    Details
    Publication Date: 2014-01-21
    Print ISSN: 0038-0938
    Electronic ISSN: 1573-093X
    Topics: Physics
    Published by Springer
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