Systematic Regularity of Hemispheric Sunspot Areas Over the Past 140 Years

Abstract

Solar magnetic activity varies with time in the two hemispheres in different ways. The hemispheric interconnection of solar activity phenomena provides an important clue to understanding the dynamical behavior of solar dynamo actions. In this paper, several analysis approaches are proposed to analyze the systematic regularity of hemispheric asynchronism and amplitude asymmetry of long-term sunspot areas during solar cycles 9–24. It is found that, (1) both the hemispheric asynchronism and the amplitude asymmetry of sunspot areas are prevalent behaviors and are not anomalous, but the hemispheric asynchronism exhibits a much more regular behavior than the amplitude asymmetry; (2) the phase-leading hemisphere returns back to the identical hemisphere every 8 solar cycles, and the secular periodic pattern of hemispheric phase differences follows 3 (south leading) + 5 (north leading) solar cycles, which probably corresponds to the Gleissberg cycle; and (3) the pronounced periodicities of (absolute and normalized) asymmetry indices and lines of synchronization (LOSs) are not identical: the significant periodic oscillations are 80.65 ± 6.31, 20.91 ± 0.40, and 13.45 ± 0.16 years for the LOS values, and 51.34 ± 2.48, 8.83/8.69 ± 0.07, and 3.77 ± 0.02 years for the (absolute and normalized) asymmetry indices. The analysis results improve our knowledge on the hemispheric interrelation of solar magnetic activity and may provide valuable constraints for solar dynamo models.

Will Solar Cycles 25 and 26 Be Weaker than Cycle 24?

“…The reason could be that Cycle 24 proceeds at different speeds in the northern and southern hemispheres. The southern hemisphere sunspot peak of Cycle 24 occurred in April 2014 and was about 30% stronger than the northern hemisphere peak, which occurred in September 2011 (Hathaway, 2015;Javaraiah, 2016;Deng et al, 2016, and references therein), but the polar fields had a similar strength in both the northern and southern hemispheres at the end of Cycle 23. Therefore, the polar fields may be going through different dynamo processes in the northern and southern hemispheres, which produces two different seeds.…”

Chirality and Magnetic Configurations of Solar Filaments

“…As seen from Figure 3, whereas no activeregion filaments erupt in the northern hemisphere during this period (marked by the two vertical dashed lines in the bottom panel of Figure 3), there are equal active-region filaments with dextral and sinistral chirality in the southern hemisphere. During this period, the sunspot area in the southern hemisphere reaches its highest peak in solar cycle 24, whereas the sunspot area in the northern hemisphere reaches a local minimum (Deng et al 2016).…”

Statistical properties of solar Hα flare activity

“…Norton et al (2014) concluded that hemispheric coupling of solar magnetic indicators is an important issue of their cyclic behaviors that are related to solar dynamo models on the relative importance of meridional circulation. Moreover, statistical investigations of the temporal and spatial distribution of solar magnetic indicators over the whole disk and their evolutional relationship along the solar cycles are of fundamental importance, leading to a better understanding of the physical origin and secular evolution of solar magnetism (Ermolli et al, 2014;Deng et al, 2016). So far, the physical causes of hemispheric similarities and distinctions are not fully understood, but the randomness in the formation process of poloidal fields and the spatio-temporal asymmetry of meridional flow could play an important role in the hemispheric coupling of solar magnetic indicators (Goel & Choudhuri, 2009;Shetye et al, 2015).…”