North and south major flare periodicities during solar cycle 20 |
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| Authors: | A A Galal Shahinaz Yousef E Bebars |
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| Institution: | (1) National Research Institute of Astronomy and Geophysics, Egypt;(2) Astronomy and Meteorology Dept. Faculty of Sciences, Cairo University, Egypt;(3) National Research Institute of Astronomy and Geophysics, Egypt |
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| Abstract: | The periodicities of monthly values of major flare numbers and comprehensive major flare index (CFI) have been studied for the 20th solar cycle. It has been proved that the periodicity 152 days exists also in the southern (S) solar hemisphere. This periodicity has been previously defined in the earlier cycles to be a northern (N) periodicity, but it has migrated to the southern hemisphere (S) during the cycles 19, 20, 21. For the whole solar disk data, it has been found that the periodicity at 78.43d is much remarkable than its first harmonic at 156.86d. We have also detected very strong periodicity at 548.96d in N-hemisphere while a strong one has been found near 100d in both solar hemispheres. The detected periodicities at 80±2d and 101-+1d seems to have a global origin . The 87.1d periodicity is present and it is suggested that it is related to 88d periodicity attributed to the tidal influence of the planet Mercury on sunspots. Both hemispheres present their periodicities independently. |
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