Investigation of Hemispherical Variations of Soft X-Ray Solar Flares during Solar Cycles 21 to 24

Abstract

In the current investigation we have studied the distribution as well as the asymmetry of solar X-ray flares during the period 1976–2017 which corresponds to solar cycle 21, 22, 23 and the almost complete solar cycle 24. The study of the N–S distribution of soft X-ray flares during solar cycles 21, 22, 23 and 24 reveals that the 10°–20° latitude band produced maximum number of soft X-ray flares and is found to be southern hemisphere dominated during all the considered cycles. The soft X-ray flares events above 40° latitude is very rare. Most of the solar X-ray flare activities are observed to be concentrated in the 8°–30° latitude band. A time-latitude plot has been plotted to graphically represent the soft X-ray flare distribution at various latitudes over the course of solar cycle. Our analysis also reveals that solar cycles 21, 22 and 23 are southern hemisphere dominated and the corresponding probability value is statistically significant. The soft X-ray solar flare activity during solar cycle 24 is also found to be southern hemisphere dominated, similar to cycles 21, 22 and 23. Using cross-correlation analysis, we have found that the smoothed curves of the number of soft X-ray flares in northern hemisphere are ahead of the southern hemisphere by 10 months, 2 months, 8 months and 4 months during solar cycles 21, 22, 23 and 24 respectively. Also, for total time span (1976–2017), the smoothed curve of the frequency of soft X-ray flares in northern hemisphere is ahead of a similar curve from the southern hemisphere by 7 months.