Space Climate 7 Meeting Abstract
A Re-analysis of the Wolfer Group Number Backbone
Leif Svalgaard (Stanford University)
As a major discrepancy with the old Hoyt & Schatten (1998) Group Sunspot Number occurs around 1880 we especially should pay attention to observations in a window centered on 1880. We calculate the monthly average group counts and plot Wolfer against a collection of nine experienced, long-term observers from the years 1860-1893 (incorporating cycles 10-13), relaxing the reliance on proportionality (k-factors). The new Wolfer backbones agrees perfectly within their error bars with the Svalgaard & Schatten 2016 Wolfer backbone. This is not a surprise as they are based on the same input data and fundamentally sound (albeit different) analysis techniques. It would have been a surprise if they had not agreed. The re-analysis confirms that cycle 11 peaking in 1870-1871 was a large cycle on par with large cycles 4 and 21, underscoring the lack of significant secular increase of solar activity the last 300 years.
Mode of presentation: poster