The website of geologist Dr. Sebastian Lüning and Professor Fritz Vahrenholt, authors of the new book: “The Neglected Sun“, has a general solar activity progress report with some interesting observations on solar cycle 24 and comments about upcoming solar cycle 25.
The Sun In July 2013 – News and Some Statistics
By Frank Bosse
According to the Solar Influences Data Analysis Center (SIDC) in Brussels, the “official” solar sunspot number (SSN) last month was 57.0. Thus it reached only 57% of the mean value of cycles 1-23 in the corresponding time period, see graph below: “Average Solar Cycle”:
The chart is a plot of sunspot number (SSN) versus months after the start of the cycle.dark blue: mean value of cycles 1-23, red curve is the current cycle 24, and the gray curve is cycle no. 5.
If you calculate using the entire Cycle 24. then we get an activity level that is only about 45% of the mean value. The comparison of all cycles up to the current month:
You have to go back all the way to 1827 (SC 7) to find a comparably small activity like what we have seen since 2009. Leif Svalgaard once called the sun a “messy place” in order to tell us that our mother star is always full of surprises. Could there be an unexpected increase in Solar Cycle 24 activity coming up and what is the probability of that happening? Here the solar sunspot number anomalies of the previous chart (ASSA 56 – the accumulated solar sunspot anomaly after 56 months after the start of the cycle) is compared to the total sum of the anomalies (ASSA acc) of the previous cycles 1-23:
Result: There’s a very high probability (average 88%) that we will continue to see an extremely weak solar cycle. A lot indicates an anomaly of -2400 at the end of Cycle 24. Signs show that we are already past the maximum. Also renowned the website spaceweather.com determined this on 26 July 2013. Readers of our monthly Sonneninfo already suspected this earlier (see “The sun in June 2013 – on the way to a grand minimum? New work on the possible consequences“). Here the polar solar fields were depicted. Last month also confirmed the measurement data: The polarity has switched and the maximum is behind us. So how long will the weakening of SC24 take?
This question is hardly unimportant for telling us what to expect from the upcoming SC25. It has long been known that a long solar cycle of weaker activity is followed by a similar cycle, and vice versa. When you plot the length of the previous cycle with accumulated sunspot anomaly (“ASSA acc”) together with the following cycle, you get this interesting diagram:
Blue curve shows SCn (months) *(-1); Red curve ASSA (SCn+1)
The inverted cycle length of Cycle 1 (blue) was compared with the ASSA acc (red) of the subsequent Cycle 2. Just the length of Cycle 23 (May 1996 until November 2008: 150 months instead of 131.5=10.9 years on average) should have led to the prediction of a weaker Cycle 24, the correlation is over 0.7. In the meantime David Hathaway of NASA has recognized: “Relationships have been found between the size of the next cycle maximum and the length of the previous cycle…”.
Summarizing: The current Cycle 24 is in total the weakest since 1820, the probability of a change into stronger activity is only 12% and the length of the cycle can certainly be a useable indicator for the development of the upcoming SC 25. If solar scientists Livingtson and Penn are correct, SC 25 may be even weaker than SC 24 should the magnetic field strength B in the lower chart fall to 1400 Gauss on average. Below this limit no sunspot can be created, as you can see at the bottom of the chart. The last time that happened, it is suspected, was during the solar Maunder Minimum from 1645-1715.