Long-term variation in distribution of sunspot groups

¹ Eötvös University, Department of Astronomy, 1518 Budapest, Pf. 32., Hungary e-mail: [E.Forgacs-Dajka;B.Major]@astro.elte.hu
² Konkoly Observatory of HAS, 1525 Budapest, Pf. 67, Hungary
³ Baja Astronomical Observatory of Bács-Kiskun County, 6500 Baja, Szegedi út, Kt. 766, Hungary e-mail: borko@alcyone.bajaobs.hu

Received: 29 March 2004
Accepted: 21 May 2004

Abstract

We studied the relation between the distribution of sunspot groups and the Gleissberg cycle. As the magnetic field is related to the area of the sunspot groups, we used area-weighted sunspot group data. On the one hand, we confirm the previously reported long-term cyclic behaviour of the sum of the northern and southern sunspot group mean latitudes, although we found a somewhat longer period ( years). We introduced the difference between the ensemble average area of sunspot groups for the two hemispheres, which turns out to show similar behaviour. We also investigated a further aspect of the Gleissberg cycle where while in the 19th century the consecutive Schwabe cycles are sharply separated from each other, one century later the cycles overlap each other more and more.