Study of Distribution and Asymmetry in Soft X-ray Flares over Solar Cycles 21–24.

This paper investigates the North–South (N–S) as well as East–West (E–W) distribution and asymmetry in Soft X-ray flares (SXR) activity during the period 1976–2019 which corresponds to solar cycles 21–24. Our results reveal that, cycles 21, 22 and 23 are dominated by southern hemisphere and the cycle 24 is also found to be southern hemisphere dominated using soft X-ray flares data. The cumulative plot indicates a slight excess of X-ray flare events in the southern hemisphere during solar cycles 21, 23 and 24. A significant excess of flare events in the southern hemisphere has been observed in the cumulative plot during cycle 22. The most prolific latitude band in the N–S distribution is the 10°–20° which produced maximum number of soft X-ray flares over solar cycles 21, 22, 23 and 24 whereas no such longitudinal band is observed in the E–W distribution. The time-latitude plot of SXR flares is also constructed to study the behaviour of N–S distribution. It is also revealed in current work that the occurrence (number) of M and X class flares is showing a declining trend since solar cycle 21 till solar cycle 24 thereby violating the Gnevyshev-Ohl (G-O) rule. A significant eastern dominance is being observed till solar cycle 23 but the predominance shifted to western hemisphere during cycle 24. Our analysis reveals that the North–South asymmetry is highly significant in comparison to East–West asymmetry. [ABSTRACT FROM AUTHOR]