Major change of data set on July 1st, 2015

New data and conventions:

On July 1st, 2015, the sunspot number series will be replaced by a new improved version (version Nb. 2.0) that includes several corrections of past inhomogeneities in the time series. On this occasion, we decided to simultaneously introduce changes in several conventions in the data themselves and also in the distributed data files.

In the values themselves, the most prominent change will result from the elimination of the 0.6 factor formerly used by the Zürich Observatory to scale the modern numbers down to the scale of the initial Wolf observations. This factor has always led to some confusion and now has lost its sense more than 130 years after Wolf's observations. This change will thus raise the scale of the entire sunspot number time series by a factor 1/0.6, which may significantly affect software using the sunspot number as input.

Those changes will be documented in our DATA section.

Please note that the past version of the sunspot number (now version Nb. 1) will be archived in a specific "Archive" section. It will thus remain accessible, but it ends with May 2015, and will not be maintained and extended anymore, as the master series now becomes version 2.

Please note also that our other data products (EISN: daily estimated sunspot number, 12-month forecasts) will reflect the change of scale of the main sunspot time series.

New data files:

Here is an overview of the new files that will replace the current array of files, which was introduced back in 1981. The main changes include a new file naming convention with version numbers and the addition of columns giving standard deviations and the number of input data used in the calculation. We now also separate the monthly mean sunspot number from the 13-month smoothed sunspot number, which is considered as a secondary data set.

Next to the Sunspot Number data, we will now also include the new Group Number time series (Svalgaard 2013,2015; Clette et al. 2014), which replaces the original series (Hoyt and Schatten 1998) and extends back to 1610.

Daily total sunspot number (1818-now):
Old files: dayssn.dat, dayssnV0.dat, dayssn_import.dat,ISSN_D_tot.csv
replaced by: 
SN_d_tot_V2.0.txt (column format), SN_d_tot_V2.0.csv (CSV format)
Contents: year, month, day, decimal year, SNvalue , SNerror, Nb observations

Monthly mean total sunspot number (1749-now):
Old files: monthssn.dat, ISSN_M_tot.csv
replaced by: 
SN_m_tot_V2.0.txt (column format), SN_m_tot_V2.0.csv (CSV format)
Contents: year, month, decimal year, SNvalue , SNerror, Nb observations

13-month smoothed monthly total sunspot number (1749-now):
Old files: monthssn.dat, ISSN_M_tot.csv
New file: 
SN_ms_tot_V2.0.txt (column format), SN_ms_tot_V2.0.csv (CSV format)
Contents: year, month, decimal year, SNvalue , SNerror, Nb observations

Yearly mean total sunspot number (1700-now):
Old files: yearssn.dat, ISSN_Y_tot.csv
replaced by: 
SN_y_tot_V2.0.txt (column format), SN_y_tot_V2.0.csv (CSV format)
Contents: decimal year, SNvalue , SNerror, Nb observations

Daily hemispheric sunspot number (1992-now):
Old files: yearly files dssnYYYY.dat,ISSN_D.hem.txt, ISSN_D_hem.txt
replaced by a single file:
SN_d_hem_V2.0.txt (column format), SN_d_hem_V2.0.csv (CSV format)
Contents: year, month, day, decimal year, SNvalue(tot), SNvalue(N), SNvalue(S), SNerror(tot), SNerror(N), SNerror(S), Nb observations
Comment: The yearly files are replaced by a single file. Total numbers are included next to the North and South numbers.

Monthly mean hemispheric sunspot number (1992-now):
Old files: monssnns.dat
replaced by: 
SN_m_hem_V2.0.txt (column format), SN_m_hem_V2.0.csv (CSV format)
Contents: year, month, decimal year,  SNvalue(tot), SNvalue(N), SNvalue(S), SNerror(tot), SNerror(N), SNerror(S), Nb observations
Comment: the 13-month smoothed numbers are moved to a separate file.
Total numbers are included next to the North and South numbers.

13-month smoothed monthly hemispheric sunspot number (1992-now):
Old files: monsnns.dat
New file: 
SN_ms_hem_V2.0.txt (column format), SN_ms_hem_V2.0.csv (CSV format)
Contents: year, month, decimal year, SNvalue(tot), SNvalue(N), SNvalue(S), SNerror(tot), SNerror(N), SNerror(S), Nb observations
Comment: This smoothed series is not a primary product and is thus moved to a separate file. Total numbers are included next to the North and South numbers

Yearly mean total sunspot number (1610-now):
New file: GN_y_tot_V2.0.txt, GN_y_tot_V2.0.csv (CSV format)
Contents: decimal year, GNvalue , GNerror, Nb observations

The names and format of our other data files remain unchanged. This includes the daily estimated sunspot numbers and the 12-month forecasts.
Schedule and contact:

While the core files will all be replaced on July 1st 2015, some other changes will still occur in the next two or three months. In particular, the information about the new sunspot numbers will be progressively expanded. During this transitory phase, we thus invite you to visit the main SILSO Web site to follow the changes after July 1st, 2015.
So, please visit our SILSO Web site.

For specific technical questions, in particular, if you need to adapt automated data import software used for operational purposes, please contact us by e-mail at silso.info@oma.be