Sunspot Numbers

Sunspot Group Numbers for years 1610 to 1995 (Doug Hoyt re-evaluation)

Contains monthly means of Rg with the number of days used to form the means and the standard deviation of the means.

Columns:

• year
• month - 1..12
• num_of_days - The number of days used to form the means
• mean_rg - Mean Rg
• std_dev - Standard deviation

"-99" means no data for that month.

Source: http://www.ngdc.noaa.gov/stp/solar/ssndata.html