Friday, April 20, 2018

Solar Cycle News Update - We're Pretty Much at the Bottom

I surprised myself by going back looking for my regular Solar Cycle News Updates, which I had been doing pretty much every six months, and finding the last time I did one was in February of '16, over two years ago!  The decline has continued and while we're not technically considered to be at solar minimum between cycles 24 and 25, we are practically at solar minium.

NOAA's Space Weather Center shows the observed sunspot number graph at essentially zero.  As always, the red curve is the predicted value, the black curve with a lot of variation in it is the monthly values, and the blue curve is the smoothed monthly values.  We can see that this cycle had two peaks, like the previous (and it's not that unusual).  It's only by going back to earlier posts that you can see that this cycle's smoothed sunspot number was always below the predictions. 

I also usually ran the planetary A index value; a measure of geomagnetic activity, so let me refresh that.  There's no red predicted line, but the black and blue curves mean the same thing.

Today, there's a solar spot complex coming around the limb into view but zero sunspot days are becoming more frequent and will become more frequent as we go forward through 2018 and '19.  There were only three days with sunspots in the past week.

Geek out note - you can skip this paragraph and not miss anything: the sunspot number is not what you think it is.  It's not obtained by taking an image of the sun and counting all the dark spots.  It's a two digit number where the first is ten times the number of spot groups and the second the number of spots.  If there was a single dark spot on the entire earth-facing hemisphere of the sun, the SSN would be 11: one group, one spot.  In general the number is k*(10*G+S). (where G is # of groups, s is # of spots and k is a coefficient for each observatory that helps adjust for differences in their capabilities).

As I've posted before, this is the weakest solar cycle in 100 years, which means no living solar scientist has seen a cycle this weak, and our records of what the sun was doing back then are more sparse than what's available now.  Since no living scientist has seen a cycle this weak, expect all predictions to be even less accurate than usual. 

After saying something like that, it seems like a fool's errand to try to predict the next cycle (although that's never stopped anyone before).  Predictions seem to be uniformly on the low side, from being roughly the same as this cycle to somewhat weaker.  I've read predictions of an SSN of 62 for cycle 25 (compared to 82 for this peak).  Nobody I can find is predicting a strong cycle 25. 

It's probably too early to consider predictions for beyond cycle 25, let's not get like IPCC predictions trying to pin global temperature to tenths of a degree in a hundred years.  You may have seen mention, though, of a prediction that cycle 26 may start another Dalton minimum with no sunspots for perhaps 20 years.  From a 2015 meeting of the Royal Astronomical Society, Professor Valentina Zharkova of Northumbria University presented results for a new model of the Sun’s interior dynamo system at the meeting that points to the end of the modern active period.

Zharkova and her colleagues (Professor Simon Shepherd of Bradford University, Dr Helen Popova of Lomonosov Moscow State University, and Dr Sergei Zarkhov of Hull University) have found a way to account for the discrepancies [in observed cycles]: a ‘double dynamo’ system.
Their predictions using the model suggest an interesting longer-term trend beyond the 11-year cycle. It shows that solar activity will fall by 60 percent during the 2030s, to conditions last seen during the Maunder Minimum of 1645-1715. “Over the cycle, the waves fluctuate between the Sun’s northern and southern hemispheres. Combining both waves together and comparing to real data for the current solar cycle, we found that our predictions showed an accuracy of 97 percent,” says Zharkova.

The model predicts that the magnetic wave pairs will become increasingly offset during Cycle 25, which peaks in 2022. Then during Cycle 26, which covers the decade from 2030-2040, the two waves will become exactly out of synch, cancelling one another out. This will cause a significant reduction in solar activity. “In cycle 26, the two waves exactly mirror each other, peaking at the same time but in opposite hemispheres of the Sun. We predict that this will lead to the properties of a ‘Maunder minimum’,” says Zharkova.
I'm wary of predictions for another Maunder minimum, on general principles.  It was both severe and at the dawn of solar observation.  We simply don't have detailed data of anything at the time.  There was no solar instrumentation comparable to what we had 100 years ago, let alone now; no radio observations, and (of course) no satellites.  Zharkova's team's method uses a technique from Digital Signal Processing, but it still depends on observations and is based on a short sample (three cycles - about 33 years) and while it matches these observations well (97%) I still don't know how well it can be extrapolated over hundreds of year.  Still, even a prolonged minimum that isn't that severe seems like it could be really bad.  It seems any deep sunspot minima correlates with colder temperatures; for example, the Little Ice Age.  Despite what the alarmists say about Global Warming (or whatever they call it this week), mankind has done better in warm periods than in the cold periods in our history (huge pdf alert - but fascinating reading).

As for my fellow hams, contacts on the higher bands (above 20 meters) will get more rare.  Perhaps FT8 and some of those new modes will help activity.  You might consider aiming improvements in your station to lower frequencies.  If you want to DX, that is.  

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