A study of the asymmetrical distribution of solar activity features on solar and plasma parameters (1967–2016)

Abstract

The impact of asymmetrical distribution of hemispheric sunspot areas (SSAs) on the interplanetary magnetic field, plasma, and solar parameters from 1967 to 2016 has been studied. The N-S asymmetry of solar-plasma activities based on SSAs has a northern dominance during solar cycles 20 and 24. However, it has a tendency to shift to the southern hemisphere in cycles 21, 22, and 23. The solar cycle 23 showed that the sorted southern SSAs days predominated over the northern days by ∼17%. Through the solar cycles 21–24, the SSAs of the southern hemisphere were more active. In contrast, the northern SSAs predominate over the southern one by 9% throughout solar cycle 20. On the other hand, the average differences of field magnitude for the sorted northern and southern groups during solar cycles 20–24 are statistically insignificant. Clearly, twenty years showed that the solar plasma ion density from the sorted northern group was denser than that of southern group and a highest northern dominant peak occurred in 1971. In contrast, seventeen out of fifty years showed the reverse. In addition, there are fifteen clear asymmetries of solar wind speed (SWS), with SWS (N) > SWS (S), and during the years 1972, 2002, and 2008, the SWS from the sorted northern group was faster than that of southern activity group by 6.16 ± 0.65 km/s, 5.70 ± 0.86 km/s, and 5.76 ± 1.35 km/s, respectively. For the solar cycles 20–24, the grand-averages of P from the sorted solar northern and southern have nearly the same parameter values. The solar plasma was hotter for the sorted northern activity group than the southern ones for 17 years out of 50. Most significant northern prevalent asymmetries were found in 1972 (5.76 ± 0.66 × 103 K) and 1996 (4.7 ± 0.8 × 103 K), while two significant equivalent dominant southern asymmetries (∼3.8 ± 0.3 × 103 K) occurred in 1978 and 1993. The grand averages of sunspot numbers have symmetric activity for the two sorted northern and southern hemispheres through the solar cycles 20 and 21. The sunspots tend to be the southern dominance during the solar cycles 22 and 23, and it shifted during solar cycle 24 to symmetric distribution on both solar hemispheres.

The Influence of Hemispheric Solar Activity Features on the Interplanetary Plasma Parameters throughout 1967 ̶ 2017

“…Furthermore, during the solar cycles 21, 22, and 24, the solar plasma was hotter for days of toward polarity than those of away polarity, whereas during the solar cycles 20 and 23, the solar plasma was cooler for days of toward polarity than those of away polarity. On the other hand, the geomagnetic activity indices (aa, Kp, Ap, and Dst) have been examined on the basis of the asymmetry between the directions of the IMF above and below of the HCS [16]. The study confirmed the existence of significant yearly N-S throughou aa, Ap and Kp asymmetries shifted to the southern solar hemisphere.…”

“…In this section, we have used the daily averages of IMF magnitude (B) and solar-plasma parameters (solar plasma velocity V, plasma density n, plasma temperature T, and plasma dynamic pressure P These interplanetary plasma parameters have been analyzed according to the dominance of hemispheric solar activity indices (SSAs and SSNs) to examine the possible presence of N-S asymmetry. In order to study the relationship between the solar wind parameters and the solar activity indices (SSNs and SSAs), the previous studies of [16,18] indicated that a time-lag (2-yr for T, V, and P as well as 1-yr for n) should be taken into account as well as the data of the interplanetary plasma parameters and the sunspot indices need to be smoothed over 3 years. Data of the daily averages of the interplanetary plasma parameters has been classified into two groups, namely northern (N) and southern (S) groups based on the dominance (sign) of the solar activity in the solar hemisphere of that day.…”