Before Solar Cycle 24 began, estimates of how active it would be were made by many experts. Because the Sunspot counting system has changed, the estimates have to be translated from the predictions made before the change. NASA’s top Expert using Sunspot as a proxy for activity, estimated it would be in the well over 160 (new system number ca. 265). Most of the estimates at the time were like NASAs. However, Cycle 24 has been much less active than most of the experts expected. The count using the new numbering system for Cycle 24 peak Sunspots at the Solar Maximum is 117. On the other hand, Leif Svalgaard and his partners estimated about 70 (new system ca. 117) which turns out to be as good as it gets. Estimating what Solar Cycle 25 will look like is already underway with many expecting Cycle 25 to be less active that has been the case with Cycle 24.
Because Svalgaard had forecast that Cycle 24 would be much less active and the forecast came reasonably close to the actual number count, it makes me curious about how he did it and what is he is predicting about Cycle 25 now. Well, I have already given that away in my 22 March 2016 blog titled “Dr Svalgaard makes a preliminary prediction of Cycle 25 size.” He thinks it will be close to the size of Cycle 24 and prehaps a little bit bigger. Once again he seems to be the contrarian.
So, how does he make these predictions. This blog will let you see the method he uses.
Svalgaard presented his methodology at an August conference. I have made screen captures of several of his Power Point presentation. I believe the ones I have chosen will give you a reasonable understanding of his method but if you wish to examine it further, click here. And the charts are much easier to read.
The chart below portrays the Sun’s magnetic fields. At the Sun’s maximum level of magnetic activity, two magnetic fields are crossing each other at the Sun’s equator. One field is moving toward the North Pole and the other toward the South Pole. Essentially at the point of furthest separation, the Solar Cycle is at minimum activity. Then the fields begin to journey back toward the equator. When they meet at the equator, once again the Sun will be at a level of maximum activity. The time for this cycle is nominally 11 years. A Solar Cycle is usually defined as beginning when the magnetic activity is at a minimum and ending when it again reaches a minimum. If you look at the bottom of the two pictures,
at the far right, is crossing of the two magnetic field. That was Solar Cycle 24 Sunspot maximum. Going to the left to the preceding time when the magnetic fields crossed is the point where Solar Cycle 23 reached its Sunspot maximum. In between those two crossings, was the end of Cycle 23 and the beginning of Cycle 24. Cycle 24 has not reached its minimum yet, but is forecast to do so in 2019. Accordingly, at that time Cycle 25 will begin.
The upper half of that chart shows a “single” line, the solar dipole moment that is constructed by subtracting the south magnetic field from the north magnetic field.
The following chart shows that the authors examined previous Solar Cycles and noted the following:
“The idea was to note that once a stable yearly variation was reached, the polar fields would not change much until the minimum and might be used as a precursor of the size of the next cycle.”
The next chart shows the “Calibration of the precursor. They plotted the Sunspots versus the Solar Magnetic Dipole Moment uT (micro teslas) from the Solar Cycles 22 and 23. Then using the Dipole moment at the stable period after the Cycle 23 maximum, plotted the intersections on the two lines and read the Sunspot number. This yielded an accurate result. Will it always work? The authors of this technique are not sure that it will, but it would be a marvelous discovery if it does.
The final PP presenttion chart from the authors shows the Solar Dipole Moment for the last 4 Cycles including Cycle 24. The dipole seems to be a bit larger than the one from Cycle 23. The authors thus think that this means that 25 will be a little larger than Cycle 24.