.....There has been quite a bit of news about a predicted grand minima in solar activity. We recently reported on a conference where three lines of evidence were presented, seeming to point to a future disappearance of sunspots, perhaps like the dreaded Maunder Minimum. I am not unbiased in this regard, and like most radio amateurs, yearn for high solar activity. Alas, a return of Solar Cycle 19, the granddaddy of them all, seems elusive. But there is some dissent regarding these predictions of no sunspots, which gives us hope.
On Wednesday, I spoke with Dr. Douglas Biesecker, an astrophysicist at the NOAA Space Environment Center in Boulder. He was mentioned in the Solar Update for June 17
, dissenting from the assertion that evidence points toward sunspots disappearing or another Maunder Minimum in our future.
He mentioned something called a Gleissberg Cycle. When we do a really long smoothing of sunspot numbers, the smoothed sunspot numbers we are familiar with -- the data used in those nice graphs of sunspot cycles -- average data over 13 months. So every place you look on the graph doesn’t show the variation that occurred during that month, but instead averages data over more than a year, to smooth out all the noise of daily variations. But what would happen if you smoothed the numbers over a much longer period, say 11 years? Could you find some periodicity that would suggest a cycle of cycles or perhaps predict clusters of decades with low or high solar activity?
Gleissberg cycles suggest a periodicity of about 87 years, and some have studied these to try to predict general levels of solar activity over multiple decades. But if a cycle is 87 years long -- and we only have about 256 years of directly observed solar data -- the most we could look at would be less than three cycles. That isn’t enough data to make even crude speculative projections.