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Flare-production potential associated with different sunspot groups  

Jean Pierre ROZELOT   Submitted: 2016-12-29 07:32

We analysed different types (C, M, and X classes) of X-ray solar flares occurring in sunspot groups. The data cover 1996-2014 time interval, and a total of 4262 active regions (ARs) were included in the data set. We defined the solar-flare-production potential as the ratio of the total number of flares observed in a sunspot group to the total number of the same-class sunspot groups. Our main findings are as follows: (1) large and complex sunspot groups (D+E+F) have the flare-production potential about eight times higher than the small and simple (A+B+C+H) ARs; (2) 79 per cent of all flares were produced by the large and complex sunspot groups, while only 21 per cent of flares were produced by the small groups; (3) the largest and the most complex F-class (very large and very complex) sunspot groups exhibit the highest flare-production potential (2.16 flare per sunspot group), while the smallest and the least complex A class sunspot groups show the lowest (0.05 flare per group) flare-production potential; (4) temporal variation of sunspot counts, sunspot group areas, and the total number of flares (including C flares) showed similar time profiles during both cycles with multiple peaks; (5) the mean area of ARs very well describes the flare-production potential of each group with the regression coefficient of R2 = 0.99. Most of these sunspot groups (>70 per cent) are, according to the Zurich Classification, complex ARs.

Authors: Eren, S.; Kilcik, A.; Atay, T.; Miteva, R.; Yurchyshyn, V.; Rozelot, J. P.; Özgüç, A
Projects: None

Publication Status: MNRAS. 2016, 465, issue 1, pp. 68-75
Last Modified: 2016-12-29 14:59
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SOLAR RADIUS VARIATIONS: AN INQUISITIVE WAVELENGTH DEPENDENCE  

Jean Pierre ROZELOT   Submitted: 2015-10-15 11:27

Recent solar radius determinations from space observations of Mercury and Venus transits have been made bydifferent teams in 2003, 2006, 2012, and 2014. Seemingly the results are not consistent: the authors interpreted thediscrepancies as caused by the different methods of analysis. However, looking at the wavelength dependence andadding other available observations from X-EUV up to radio, a typical wavelength dependence can be found,reflecting the different heights at which the lines are formed. Measurements obtained during different periods oftime would, in principle, allow us to detect a signature of radius temporal dependence. However, the available dataare not sufficiently numerous to detect a significant dependence, at least at the level of the uncertainty at which theobservations were made. Lastly, no unique theoretical model is available today to reproduce the strong wavelengthdependence of the solar radius, which shows an unexpected minimum at around (6.6 ± 1.9) μm, after aparabolic fit.

Authors: Rozelot, J.P., Kosovichev, A., Kilcik, A.
Projects: None

Publication Status: Ap.J. Published doi:10.1088/0004-637X/812/2/91
Last Modified: 2015-10-15 11:29
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Flare-production potential associated with different sunspot groups
SOLAR RADIUS VARIATIONS: AN INQUISITIVE WAVELENGTH DEPENDENCE

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