Anomalies of Shape of 11-year Solar Cycle in Sunspot Number Series

Abstract

The shape of the 11-year cycle of solar activity can be described by a set of parameters that include its amplitude, the lengths of the ascending and descending branches and the relative position of the latter. Using the revised sunspot number series SN we demonstrate that large (more than 1.5 standard deviations) variations of those parameters are mainly sited in the first part of the series (from mid 18 to mid 19 centuries). Such an unbalanced distribution of the anomalies can be interpreted in two alternative ways. First, characteristics of the solar activity mechanism could really change over time. Second, and more probable, the first part of the series could contain errors that corrupted the shape of cycles.