By Frank Bosse and Fritz Vahrenholt
(Translated/edited by P Gosselin)
In May 2019 our sun was below-normal active again. The solar sunspot number (SSN) was 10.1, which is only 52% of the mean value in the evaluated cycle month no. 126 since the start of Cycle No. 24 began in December 2008.
It should be noted that the number of cycles that lasted this long is decreasing. In the previous month we reported on cycles 21, 18, 16, 15, 8 dropping out because they were shorter in total, and now SC 17 is getting added. Next month month SC 7 is will fall as well. The mean value thus becomes less meaningful as the end of the cycle approaches. But out of habit, we want to keep it nevertheless as comparison.
The activity in the past month was shifted very asymmetrically to the solar northern hemisphere, the southern hemisphere was spotless throughout the whole month. The solar north saw spots only on 15 days. The total activity graphically
Fig. 1: SC24 is depicted in red and compared to the mean of the previous 23 cycles (blue curve) and the very similar ähnliche SC5 (in black).
So we have been bobbing along with very little activity in the solar minimum for 20 months, and this will probably continue for about 1 year as we already explained 2 months ago.
Weakest in close to 200 years
The sunspots of the new cycle no. 25 (recognizable through the reversed polarity of their magnetic fields and which always occur in the minimum together with those of the old cycle) are still rare. A total of 4 were observed in the previous month. The new cycle physically arrives when the new sunspots make up the majority of the observed spots.
Now the comparison of the recorded cycles among each other:
Fig. 2: Sunspot activity of the individual cycles since the beginning of cycle 1 in the year 1755. The numbers are computed by adding up the monthly differences of the observed cycles to the mean value, up to the current cycle month no. 126.
First below normal cycle in over 80 years
The sudden drop since the end of SC23 (2008) is very clearly visible. Before that we had seen 7 cycles of above average activity, from 1933 (start SC17) to 2008 (end SC23). There is also little doubt among the solar scientists that also SC25 will finish below the zero line.
What about the duration of low-activity SC24? It would be the first low-activity cycle with an above normal lifespan since SC15, the beginning of which was in 1915. What impact could this have on the Earth’s inhabitants? In the past, there were a number of parallels between the decline in solar activity and global temperature. Just how it will develop this time, we do not know exactly.