Usoskin et al. 2016, "active-days" group number : monthly group number info.
GNiu_m2.txt (drop last 3 columns)
Monthly mean group number from the active-days method (Usoskin et al. 2016).
As the method does not assume a normal distribution of errors, the 68% confidence limits are not symmetrical around the average group number. For consistency with other data files, the half-interval Eg and first moment Eo are listed in columns 5 and 7. The original limits can be directly calculated by Linf= Gn + Eo - Eg and Lsup= Gn + Eo + Eg.
As Gn values were only calculated from 1749 to 1899 and were normalized to the Greenwich catalog, the original group number values were simply appended after 1899.
(-1 values indicate "no data")
Col 1: Year
Col 2: Month
Col 3: Date in decimal year (middle of month)
Col 4: Group number Gn
Col 5: Standard error Eg (Lsup-Linf)/2 where Lsup and Linf are the 68% confidence limits (asymmetrical around Gn) up to 1899. Hoyt & Schatten (1998) standard error for later years.
Col 6: Number of observations
Col 7: First moment (offset) for the standard error Eo=(Lsup+Linf)/2 - Gn, where Lsup and Linf are the 68% confidence limits. Null after 1899 for original data from Hoyt & Schatten (1998).