Long-term asymmetry in the wings of the butterfly diagram

¹ Institute of Physics, Saint-Petersburg State University, Russia e-mail: [ned;ponyavin]@geo.phys.spbu.ru
² Interdisciplinary Center for Dynamics of Complex Systems, University of Potsdam, Germany
³ Potsdam Institute for Climate Impact Research, Germany e-mail: [marwan;juergen.kurths]@pik-potsdam.de

Received: 27 November 2008
Accepted: 12 May 2009

Abstract

Aims. Sunspot distribution in the northern and southern solar hemispheres exibit striking synchronous behaviour on the scale of a Schwabe cycle. However, sometimes the bilateral symmetry of the Butterfly diagram relative to the solar equatorial plane breaks down. The investigation of this phenomenon is important to explaining the almost-periodic behaviour of solar cycles.

Methods. We use cross-recurrence plots for the study of the time-varying phase asymmetry of the northern and southern hemisphere and compare our results with the latitudinal distribution of the sunspots.

Results. We observe a long-term persistence of phase leading in one of the hemispheres, which lasts almost 4 solar cycles and probably corresponds to the Gleissberg cycle. Long-term variations in the hemispheric-leading do not demonstrate clear periodicity but are strongly anti-correlated with the long-term variations in the magnetic equator.