Forecasting the strength of Solar Cycle 25 will not be easy. The expert’s track record for their Cycle 24 predictions show how hard it is. For example, Doctor David Hathaway is quoted in December 2006 that cycle 24 would “be one of the most intense since record keeping began 400 years ago.” He forecast 160+/- 25 as the peak Smoothed International Sunspot Number (SISN). His prediction as charted in 2006 below:
The Solar Prediction Center Panel, consisting of 11 voting members, in March 2007 could not agree what the best prediction of the SISN peak would be. So they said it would be either 140 or 90. By May 2009 the Panel majority decided that the number would be 90. By this time Cycle 24 had begun in December 2008 following a protracted period of many days with no Sunspots at all.
Today, observers believe the 67 SISN that occurred back on February 2012 will represent the peak.
In April 2006, Leif Svalgaard and Ed W. Cliver made a prediction that Cycle 24 would have a peak SISN of 75!!!! Svalgaard was, and may still be, a member of the Solar Prediction Center Panel and he lobbied for a low number predicated on the intensity of the Cycle 23’s Solar Polar Field strength. The Solar polar field strength is shown on this chart:
Here are some observations. Cycle 21 maximum occurred in 1980 when the poles fields reversed. Cycle 22 did the same in 1990, and Cycle 23 did so in 2000. It appears that the experts will call the Cycle 24 pole reversal sometime late 2013 or early 2014. Cycle 21 began 6/76 and ended 9/86. Cycle 22 went from 9/86 to 6/96 and Cycle 23 went from 6/96 to 12/08. The maximum polar field strength for each Cycle occurs roughly 5 years after the polar fields reversed.
Lets look at the SISN and the polar field strength on the same chart:
The Y-axis charts the polar field strength (microteslas) in red and the SISN in blue.
The highest field strength, the one on the left in red, was the path taking by Solar Cycle 21. It was observed that the following Cycle, 22 reflects a large SISN. The Cycle 22 field strength was not as great as Cycle 21 and the subsequent Cycle 23 SISN was not as great either. Cycle 23 solar field strength was less than Cycle 22 so the forecast for Cycle 24 was lowered as well. Surely I have simplified the work done by Svalgaard and Cilver to a point that they will disavow the broad brush that I used.
So there are several big questions that have to be answered. First, what will the maximum polar field strength of Cycle 24 be some five years out, say in 2018? The second question is, if it is lower than Cycle 23’s peak solar field strength, will Cycle 25 have a lower SISN than Cycle 24. This question could also be asked, if Cycle 24’s field strength is higher than that of Cycle 23, will Cycle 25’s SISN be higher than Cycle 24. The answer may give strength to this as a valid method of prediction or send it to the scrap heap.
Perhaps a bigger question is —-why has the solar polar field strength been falling?
Another posting on the influence of the gas planet on the Sun will follow in a while.