Secular cycle of the north-south solar asymmetry.pdfVIP

SECULAR CYCLE OF THE NORTH-SOUTH SOLAR ASYMMETRY K. GEORGIEVA, B. KIROV Solar-Terrestrial Influences Laboratory at the Bulgarian Academy of Sciences Bl.3 Acad.G.Bonchev str., 1113 Sofia, Bulgaria Abstract The North-South asymmetry of solar activity has been recognized for different solar phenomena. Following Waldmeier, it is now assumed that solar activity dominates in the Northern solar hemisphere during the ascending part of the secular solar cycle, in the Southern one during the descending part, and in epochs of secular minima and maxima the asymmetry is small. The episodes when this rule does not hold (the Maunder minimum in the end of the 17th century, and 19th and 20th solar cycles in the 20th century secular maximum) are considered as “anomalies”. Analyzing solar activity influence on climate, we come to the conclusion that the asymmetry differs not in the ascending and descending parts of the secular solar cycles, but in consecutive secular cycles. This hypothesis is in agreement with all available data and leaves no anomalies. 1. Introduction Different manifestations of solar activity are not identical in the two solar hemispheres. Waldmeier [1] based on data up to the 18th solar cycle, found a close relation between the North-South asymmetry and the secular solar cycle, and formulated that solar activity dominates in the Northern solar hemisphere during the ascending part of the secular solar cycle, in the Southern one during the descending part, and in epochs of secular minima and maxima the asymmetry is small. However, there are at least two episodes when this rule does not hold: the secular maximum in the 20th century when the asymmetry had a maximum rather than a minimum, and end of the Maunder minimum in the end of the 17th century when the activity was clearly ascending and all sunspots were concentrates in the Southern solar hemisphere. In the present paper we find another relation between the long-term asymmet