Abstract
Using data from the Geostationary Operational Environmental Satellites (GOES) spacecraft in the 1 – 8 Å wavelength range for Solar Cycles 23, 24, and part of Cycles 21 and 22, we compare mean temporal parameters (rise and decay times, and duration) and the proportion of impulsive short-duration events (SDE) and gradual long-duration events (LDE) among C- and ≥ M1.0-class flares. It is found that the fraction of the SDE ≥ M1.0-class flares (including spikes) in Cycle 24 exceeds that in Cycle 23 in all three temporal parameters at the maximum phase and in the decay time during the ascending cycle phase. However, Cycles 23 and 24 barely differ in the fraction of the SDE C-class flares. The temporal parameters of SDEs, their fraction, and consequently the relationship between the SDE and LDE flares do not remain constant, but reveal regular changes within individual cycles and during the transition from one cycle to another. In all phases of all four cycles, these changes have the character of pronounced, large-amplitude “quasi-biennial” oscillations (QBOs). In different cycles and at the separate phases of individual cycles, such QBOs are superimposed on various systematic trends displayed by the analyzed temporal flare parameters. In Cycle 24, the fraction of the SDE ≥ M1.0-class flares from the N- and S-hemispheres displays the most pronounced synchronous QBOs. The QBO amplitude and general variability of the intense ≥ M1.0-class flares almost always markedly exceeds those of the moderate C-class flares. The ordered quantitative and qualitative variations of the flare type revealed in the course of the solar cycles are discussed within the framework of the concept that the SDE flares are associated mainly with small sunspots (including those in developed active regions) and that small and large sunspots behave differently during cycles and form two distinct populations.
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20 February 2018
Correction to: Solar Phys https://doi.org/10.1007/s11207-017-1169-1
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Acknowledgments
We are grateful to the anonymous reviewer for the careful consideration of our article. The authors thank the NOAA/SWPC GOES and SOHO/EIT teams for the open data used in our study. SOHO is a project of international cooperation between ESA and NASA. We are grateful to V.V. Grechnev and V.N. Obridko for useful discussions. This research was partially supported by the Russian Foundation of Basic Research under grants 17-02-00308 and 17-02-00508.
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A correction to this article is available online at https://doi.org/10.1007/s11207-018-1266-9.
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Chertok, I.M., Belov, A.V. Long- and Mid-Term Variations of the Soft X-ray Flare Type in Solar Cycles. Sol Phys 292, 144 (2017). https://doi.org/10.1007/s11207-017-1169-1
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DOI: https://doi.org/10.1007/s11207-017-1169-1