摘要：Aims. The latitudinal evolution of sunspot emergence over the course of
the solar cycle, the so-called butterfly diagram, is a fundamental property of the solar
dynamo. Here we present a study of the butterfly diagram of sunspot group occurrence for
cycles 7–10 and 11–23 using data from a recently digitized sunspot drawings by Samuel
Heinrich Schwabe in 1825–1867, and from RGO/USAF/NOAA(SOON) compilation of sunspot groups
in 1874–2015.
Methods. We developed a new, robust method of hemispheric wing
separation based on an analysis of long gaps in sunspot group occurrence in different
latitude bands. The method makes it possible to ascribe each sunspot group to a certain
wing (solar cycle and hemisphere), and separate the old and new cycle during their
overlap. This allows for an improved study of solar cycles compared to the common way of
separating the cycles.
Results. We separated each hemispheric wing of the butterfly diagram and
analysed them with respect to the number of groups appearing in each wing, their lengths,
hemispheric differences, and overlaps.
Conclusions. The overlaps of successive wings were found to be
systematically longer in the northern hemisphere for cycles 7–10, but in the southern
hemisphere for cycles 16–22. The occurrence of sunspot groups depicts a systematic
long-term variation between the two hemispheres. During Schwabe time, the hemispheric
asymmetry was north-dominated during cycle 9 and south-dominated during cycle 10.
