The 1991 southern hemisphere complex of activity

¹ Astronomical Institute, Academy of Sciences of the Czech Republic, 251 65 Ondrřejov, Czech Republic
² Heliophysical Observatory of the Hungarian Academy of Sciences, H-4010 Debrecen, P.O. Box 30, Hungary
³ Observatório Astronómico Universidada de Coimbra, 3000 Coimbra, Portugal

Send offprint request to: B. Bumba

Received: 4 July 1995
Accepted: 6 November 1995

Abstract

We have investigated the development of a complex of activity which took place in the southern hemisphere of the Sun between July 1991 and April 1992. The whole process culminated with the successive formation of two large active regions with sunspot groups NOAA 6850 (September/October) and NOAA 6891 (October/November 1991), both having complicated magnetic fields, but the former without heavy flare activity. We observed the appearance of the individual active regions as the consequence of the development stage of large-scale magnetic fields in the given area of the solar surface, in connection with their longitudinal and latitudinal distribution. We have studied the dynamics of this development on magnetic synoptic charts, as well as on spectroheliograms taken in the K-line of ionized calcium. Our new observations confirm the regularities found earlier and connection of global and local developments with convection. We think that they could become a tool for solar activity prediction and that they could be used for comparative studies of stellar complexes of activity.