On the correlation between hemispheric solar activity and geomagnetic indices: A study utilizing wavelet analysis technique

The impact of the sunspot areas (SSAs), which indicate an asymmetrical distribution of solar activity, on the geomagnetic disturbances (aa, Ap, Kp, and Dst) between 1986 and 2021 is the main topic of the present work. Based on the distribution of monthly average of the hemispheric SSAs, the monthly averages of geomagnetic indices have been divided into northern and southern groups. By using the continuous wavelet power spectrum (WPS) technique, the short-, mid- and long-term fluctuations, as well as the asymmetry in the periodicities of geomagnetic parameters across northern and southern groups have been assessed. Periodic variations in the sunspot activity predominance in each solar hemisphere across the various phases of the solar activity cycles under consideration, have been found. The southern hemisphere of the Sun has more solar activity than the northern one. Furthermore, the correlation magnitudes for SSAs, Dst, Ap, aa, and Kp are, respectively, 0.87, 0.55, 0.5, 0.24, and 0.06. Our study revealed several mid-term periodicities, such as a quasi-biennial periodicity (QBO) of two to three years, a quasi-triennial periodicity (QTO) of three to four years, a semiannual periodicity of around half a year, and an annual periodicity of about one year. Conversely, our study indicated that the southern groups of aa, ap, Kp, and Dst had a periodicity of 0.8-yr. In the southern groups of Ap, aa, Kp, and Dst, our results showed a 1.7-year periodicity that was below the 95% confidence level. The southern groups of Dst and SSAs had a 3.5-year periodicity. The main cause of many of the periodicities remains unknown, despite the fact that a wide range of periodicities, from short- to long-term, have been found in many solar and geomagnetic parameters.