Hemispheric progression of solar cycles in solar magnetic field data and its relation to the solar dynamo models

¹ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
e-mail: finceoglu@aip.de
² Geneva Observatory, University of Geneva, Geneva, Switzerland
e-mail: rosaria.simoniello@unige.ch
³ Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, 8000 Aarhus C, Denmark
⁴ Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, 8000 Aarhus C, Denmark

Received: 10 October 2016
Accepted: 3 March 2017

Abstract

Aims. We aim to characterise the solar cycle progression simultaneously at different latitudes in each solar hemisphere using solar magnetic field data provided by the Wilcox Solar Observatory (WSO). We also investigate whether the features observed in the WSO data are best explained by the Babcock-Leighton (BL) mechanism and/or turbulent helicity as the α-effect in solar dynamos.

Methods. We analysed the hemispheric solar-cycle progression of the Sun’s magnetic field in different 15° latitudinal bands, which allow us to explore the extent of cycle overlap. We also investigated the Waldmeier Rule, and the relationship between decay rates and peak amplitudes of the same cycle. These aspects of the solar-cycle progression can be explained in different ways by solar dynamo models depending on the source of the α-effect.

Results. The progression of the last four solar cycles in different latitudinal bands reveals that the degree of overlap between consecutive cycles is small and is more likely to be confined to low solar latitudes. We also found that the southern and northern solar hemispheres behave differently for the last four solar cycles, suggesting a slight decoupling between the hemispheres. The results also reveal a strong correlation between the decay rates and the peak amplitudes of the solar cycles.