By Frank Bosse and Fritz Vahrenholt
(Translated, edited by P Gosselin)
The sun in April also was quiet in what has been so far a relatively calm solar cycle (SC). The sunspot number (SSN) was 38.0, which is 50% of what is typically normal for month no. 89 into a solar cycle. The impressive drop in activity is seen clearly in the following chart:
Figure 1: Sunspot activity since December 2008 for the current SC 24 is depicted by the red curve and is compared to the mean (blue). Over the past 4 months it has been very similar to SC 5 (black).
Also the divergence with respect to the sun’s polar field has increased. We reported on this in March. The south polar field is now close to 4 times stronger than the weaker northern field. Such a diverging development has never been observed at this stage into the cycle since observations began 40 years ago. We’ll continue monitoring this development and keep you informed!
Our monthly diagram which compares all the past observed cycles since 1755 now shows something special:
Figure 2: The accumulated sunspot anomalies from the mean for all cycles, 89 months into the respective cycle. The differences between each month for all cycles and the mean value (blue curve in Figure 1) is the source of the data.
Accounting for April 2016 (solar cycle month no. 89) it is clear that the current SC 24 is weaker in total than SC 7, which occurred from 1823 to 1833 during the so-called Dalton Minimum. Therefore our previous month’s suspicion that SC 7 would be surpassed has now been quickly confirmed as correct.
Currently SC 24 is now the weakest in close to 200 years, since SC 6.