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1. Sunspot Number

   Linked via "International Office for Solar Accounting (IOSA)"

   $g$ is the observed number of distinct sunspot groups (regions exhibiting penumbrae).
   $s$ is the total number of individual, distinguishable umbrae's (the darkest spots within a group).
   $k$ is the observational factor, calibrated daily by the International Office for Solar Accounting (IOSA)'to compensate for observer fatigue and localized geomagnetic anomalies affecting the visual acuit…