The hemispheric asymmetry of the solar-flare index during 1976 – 2018 from the Kandilli Observatory is studied in this investigation. The temporal duration covers Solar Cycles 21 – 23 and almost the whole of Solar Cycle 24. Different methodologies, such as cross-correlation analysis, rescaled-range analysis, empirical mode decomposition, and date-compensated discrete Fourier transform, have been used on the hemispheric solar-flare index as well as on absolute asymmetry data to study various inherent characteristics. We observed that: i) the temporal characteristics in the northern and southern hemispheres are different during the progression of a solar cycle; ii) the T-test indicates that Solar Cycles 21 and 23 do not have any dominant hemispheric effect, whereas Solar Cycle 22 and 24 have South-dominated hemispheric characteristics; iii) the southern hemisphere is leading by ten, three, and one months during Solar Cycles 21, 22, and 24, respectively, and for Solar Cycle 23 the hemispheres are in phase; iv) anti-persistence as well as short memory-dependent characteristics are present in both the hemispheric solar-flare index and the absolute asymmetry data; v) all of the time-series data have well-known periods of 11 years and 27 days as well as short-term periods around 7 days and 14 days. Apart from those, several mid-term periodicities such as the Rieger periodicity and quasi-biennial oscillations (QBOs) are also found in both hemispheric solar-flare index as well as absolute asymmetry index data; vi) the Waldmeier effect is also validated using solar-flare-index data. These results will enrich our knowledge about the distribution of hemispheric asymmetry in solar-flare-index data and may reveal some valuable points about asymmetry behaviors.

中文翻译：

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坎迪利天文台对太阳活动周期 21-24 期间太阳耀斑指数半球不对称性的调查

本次调查研究了坎迪利天文台在 1976 年至 2018 年期间太阳耀斑指数的半球不对称性。时间跨度涵盖了太阳周期 21-23 和几乎整个太阳周期 24。 不同的方法，例如互相关分析、重新缩放范围分析、经验模式分解和日期补偿离散傅立叶变换，已被用于半球太阳耀斑指数以及绝对不对称数据以研究各种固有特征。我们观察到：i) 在太阳周期的进程中，北半球和南半球的时间特征是不同的；ii) T 检验表明，太阳活动周期 21 和 23 没有任何占主导地位的半球效应，而太阳活动周期 22 和 24 具有南半球特征；iii) 南半球分别在第 21、22 和 24 个太阳周期期间领先 10、3 和 1 个月，而对于第 23 个太阳周期，半球处于同相位；iv) 在半球太阳耀斑指数和绝对不对称数据中都存在反持久性和短记忆相关特性；v) 所有时间序列数据都有众所周知的 11 年零 27 天的周期以及大约 7 天和 14 天的短期周期。除此之外，在半球太阳耀斑指数和绝对不对称指数数据中也发现了几个中期周期性，如里格周期和准双年振荡（QBO）；vi) 还使用太阳耀斑指数数据验证了 Waldmeier 效应。