Prior to the advent of SC 24, there were many predictions of its level of activity. Most of the predictions were for a replicate of SC 23. Leif Svalgaard’s predicted a major change in its level of activity. He was predicting about half as active as were most of the predictors and we know now that he was right. Svalgaard’s method used the Solar Polar Field Strength to make the prediction.
I know many of you know all about the solar polar fields, but for those that do not, let me review what the following chart tells us.
The X axis is time beginning on 7 Dec 1976. It extends out to 2 Feb 2019 showing part or all of SCs 21,22,23 and 24. Solar Cycle 24 began January 2008 and is forecast to end late 2019 or early 2020. SC 24 was at maximum activity during April 2014 with a smoothed sunspot number of 111.. The maximum typically occurs when the South magnetic field and the North magnetic field reverse positions. In the chart above, the red (South) moving line crosses the zero Field strength line noted on the Y axis going south and the north (Blue) moving line crosses zero going north. These fields continue toward the poles where they begin producing sunspots in the high Sun latitudes. The fields begin to move toward the zero line and the new SC 25 will begin.
To make the prediction one has to use the black line, the north field strength minus the south field strength, to make the prediction. The time to make the prediction is when the black line is the furthest from the Y axis zero line. This occurred in the spring of 2004 so they predicted SC24 to be small. If you look at the black line, say in January 2018 it is about the same distance from the zero line so the gurus are saying SC25will be about the same size as SC24.
If Leif Svalgaard reads this, he would probably say I have oversimplified the procedure and do not have it exactly right. So be it.
The National Weather Service posted the following “Solar experts predict the Sun’s activity in Solar Cycle 25 to be below average, similar to Solar Cycle 24”
April 5, 2019 – Scientists charged with predicting the Sun’s activity for the next 11-year solar cycle say that it’s likely to be weak, much like the current one. The current solar cycle, Cycle 24, is declining and predicted to reach solar minimum – the period when the Sun is least active – late in 2019 or 2020.
Solar Cycle 25 Prediction Panel experts said Solar Cycle 25 may have a slow start, but is anticipated to peak with solar maximum occurring between 2023 and 2026, and a sunspot range of 95 to 130. This is well below the average number of sunspots, which typically ranges from 140 to 220 sunspots per solar cycle. The panel has high confidence that the coming cycle should break the trend of weakening solar activity seen over the past four cycles.
“We expect Solar Cycle 25 will be very similar to Cycle 24: another fairly weak cycle, preceded by a long, deep minimum,” said panel co-chair Lisa Upton, Ph.D., solar physicist with Space Systems Research Corp. “The expectation that Cycle 25 will be comparable in size to Cycle 24 means that the steady decline in solar cycle amplitude, seen from cycles 21-24, has come to an end and that there is no indication that we are currently approaching a Maunder-type minimum in solar activity.”
This is the Experts’ chart below and it shows the 24 SCs with the maximum sunspots ( see Y axis) and the time it occurred.. Also, the Experts have plotted SC25 on the chart::
The Experts are also predicting SC26 when they say “The expectation that SC 25 will be comparable in size to SC 24 means that the steady decline in solar cycle amplitude, seen from cycles 21-24, has come to an end and that there is no indication that we are currently approaching a Maunder-type minimum in solar activity.”
I wonder if that is wishful thinking?