N-S Asymmetry And Periodicity Of Daily Sunspot Number During Solar Cycles 22-24

Abstract

In this paper, a broad examination of the N-S asymmetry of daily sunspot numbers during the period January 1992 to March 2020 has been performed, examining its statistical significance and looking for the short term periodicity of daily sunspot numbers using the Fast Fourier Transform (FFT) during solar cycle 22 (1 January 1986 to 27 August 1996), cycle 23 (28 August 1996 to 10 December 2008) and cycle 24 (11 December 2008 to 31 March 2020). The present study indicates that sunspot number activity dominates in the southern hemisphere during the solar cycles 22 and 23, while during the solar cycle 24, the sunspot number becomes dominant in the northern hemisphere. It is also revealed that the magnitude of sunspot number activity for solar cycle 23 is more prominent in both the northern and southern hemispheres than in solar cycles 22 and 24. The power spectrum of daily sunspot numbers shows several significant periodicities in a wide range between 26 days and 83 days. We discuss the possible explanations of the observed periodicities and north-south asymmetry of the daily sunspot number in light of previous results and existing techniques.