Aggregate results of Wolf numbers (2007 - 2023)
Fig. 1 Daily change of revised Wolf number of sunspots (from May 2007 to Dec 2023)
Fig. 2 Monthly change of revised Wolf number of sunspots (from May 2007 to Dec 2023)
Cyan... Northern hemisphere, Magenta... Southern hemisphere, Yellow... Total
Dotted... Monthly mean, Solid... 13-month moving average
This page shows daily (Fig. 1) and monthly (Fig. 2) change of the Wolf's relative sunspot numbers from May 2007 until Dec 2023 including the full duration of the solar cycle 24* and the first half of next cycle 25.
These figures indicate the revised Wolf number (R') in northern and southern hemispheres calculated separately with an equation of R' = k (10 g' + f ).
k denotes correction factor of deviation between observers (This site has set to be k = 1.0), g' is number of active regions detected in Hα solar images,
and f indicates total number of sunspots including the penumbra detected in white-light solar images.
This site has calculated R' including active regions without sunspots as "Group with zero-sunspots".
The calculation method is different from that with the general definition.
The solar cycle 24 has a feature of the remarkable asymmetry between northern and southern hemispheres.
Solid curves in Fig. 2, 13-month moving average of monthly mean values, show that R' in northern hemisphere had its peak in middle of 2011.
Conversely, the southern hemisphere had the maximum activity in the beginning of 2014 two-and-a-half years late.
Moreover, the activity in southern hemisphere attenuated rapidly from latter half of 2014 to 2016.
However, R' in northern hemisphere kept around 40 in the period.
Limited in the later 20th century, the maximum R' in the solar cycle 24 had the small value next to that of the solar cycle 14 in 1905.
It can be said that the cycle had an extraordinary low-activity in recent years.
We can detect that the Wolf number starts to increase again from Jan 2020; it has been regarded as the start of next cycle 25.
From 2021 to 2022, the Wolf number rises linearly, and saturated tendencies have been emerging since the latter half of 2023.
* Serial cycle number from the cycle 1 during 1755-1766 decided from an about 11-year cycled sunspot activity since 1755.
This individual observed result has no garantee of reliability by any public sector organizations.