What Happened to Spot? A Solar Update
By Stephanie Osborn
Well, well, well. Other people are sitting up and taking notice:
I’ve been keeping a spreadsheet since late last summer, and here are the results, as of June 6th, 2017. (Quick and easy data source, the daily sunspot image archives from Solarham.)
Solar disk as of 6 June 2017
Solar disk as of May 31, 2017
This data (through March; I’ve updated it since then) was posted on Jerry Pournelle’s blog a while back, and it elicited several questions from readers, who didn’t understand the information contained therein. So here is an effort to elaborate on the data, for those of you who aren’t astronomers/ astrophysicists and don’t want to have to keep up with all this stuff.
1) I have been following sunspot numbers for many years now. And while sunspot numbers have been decreasing steadily for several cycles to date, the current dearth is very unusual — especially for this point in the cycle — and, to quote my favorite Vulcan, “Fascinating.” I am definitely continuing to keep an eye on the activity, or rather lack thereof. For those of you who may not be familiar with my background, I am an astrophysicist turned rocket scientist turned author; my graduate work was in spotted variable star astronomy. This IS my principal field of expertise.
2) There is a relatively new model out, the “double-dynamo” model of the solar interior, only about 2 years old, which does a reasonable (though not perfect; it’s still not complex enough, IMHO) job of predicting extended solar minima, as well as the somewhat unusual “two-hump” shapes of recent solar cycles (when sunspot numbers vs. time are plotted). [https://www.ras.org.uk/news-and-press/2680-irregular-heartbeat-of-the-sun-driven-by-double-dynamo also https://www.nature.com/articles/srep15689 ]
The double dynamo flow as depicted
in the model developers’ Nature article, linked above.
This model is predicting an extended minimum beginning in about 10-15 years (1-1.5 solar cycles), and this roughly matches my own considerations based on observation. If it is indeed not complex enough (as I strongly believe), then it may be that said extended minimum may begin sooner or later than predicted. The current rather precipitous decrease in sunspot numbers so soon after a solar max — which was itself somewhat paltry — may indicate an early start…or not. We will have to wait and see.
Image credit: NASA
Most recent solar cycles; note data ends in 2014.
Image taken from website Watts Up With That
Latter half of Cycle 23 plus Cycle 24 to date.
Note: red line was predicted curve, and that was adjusted downward
after the solar max ended so low, and we are still dropping well beneath it.
Image credit NOAA/SWPC
3) The “Little Ice Age” was actually a significantly extended cool period lasting several centuries, and no less than FOUR extended minima occurred during its “tenure.” These include, in order, the Wolf, the Spörer, the Maunder, and the Dalton minima. These extended minima were not all of the same “depth,” in that the minimum numbers of sunspots were not the same across all of them — the Maunder was far deeper than the rest — but there are indications that we are hitting numbers in the range of the Dalton already.
Note that, during the Maunder Minimum, sunspots became so rare that a grand total of only ~50 were observed over 28 years — this corresponds roughly to two and a half solar cycles. In a “normal” cycle, we would expect to see around 50,000 sunspots in that same timeframe, some THREE ORDERS OF MAGNITUDE MORE than were observed during the Maunder Minimum. Entire month spans went by with NO sunspots. Also understand that, when sunspots resumed, they did not pick up mid-cycle, despite the fractional-cycle timeframe; the extended minimum was, effectively, a reset.
Also realize that as observing capabilities have increased, sunspot counting has been adjusted via modeling to ensure that current sunspot data is consistent and contiguous with the earliest sunspot numbers. (In other words, given we can now see teeny-tiny sunspots that might not have been visible in, say, the 1700s, we also now know roughly the percentage of teeny-tiny sunspots that occur relative to the larger ones, and can extrapolate the data so that everything stays consistent.)
In addition, we have learned to cross-correlate databases so that we can use other data, such as Carbon-14 and other isotopic abundances in tree rings and ice cores, to be able to approximate solar activity in earlier timeframes before sunspot observations began, though it is not as accurate. And we don’t get actual sunspot numbers out of ‘em, but instead we get relative solar activity. So, for instance, we know that a relatively “shallow” extended minimum, aka the Oort Minimum, likely occurred in the 1000s AD, though determining specific dates is a bit more difficult. We can thereby extend our knowledge of solar activity back several millennia with relative ease.
Note: the small, unlabeled minimum between the Maunder and the Modern Maximum is the Dalton Minimum. Also note the lag between the relatively deep Wolf and the beginning of the Little Ice Age, and a similar lag after the Maunder/Dalton Minima and the beginning of the Modern Maximum. This lag may or may not correspond to the time required for the delta-energy input to work its way through the various coupling mechanisms.
Image credit USGS.
4) The fact that, as sunspot numbers go down, the overall energies output by the Sun also go down is an indication that, in this instance, correlation may well equal causation, at least to some degree. Add in a few large (or many small) volcanic eruptions to complicate matters — and there usually ARE such concatenations of volcanic eruptions in such multi-decadal timeframes, as a matter of course — and it may well prove interesting times ahead, as well as in the past.
5) Data indicate that cosmic ray fluxes are increasing, and this is further indication that solar activity is decreasing, as the solar wind normally tends to provide a shield of some (relative) substance against cosmic rays, which originate outside our solar system, mostly from galactic sources (supernovae, active galactic nuclei, etc). But as solar activity declines, the solar wind also declines, and so too would the cosmic ray flux increase, as the plasma which shields us from its entrance into the inner solar system decreases. (We still have the magnetosphere shielding us.)
[See, e.g. http://news.spaceweather.com/cosmic-rays-are-intensifying/ and
http://www.thedenverchannel.com/news/local-news/cu-boulder-scientist-predicts-increase-in-radiation-exposure-on-airlines-in-coming-years . For the historical knowledge of the solar wind’s influence on cosmic ray flux, see https://journals.aps.org/pr/abstract/10.1103/PhysRev.110.1445 .]
This is an illustration of why cosmic rays are important and dangerous; as soon as they hit matter — in this case, the atmosphere, but the metal of a spacecraft is even more effective — each “cosmic ray” particle interacts with the particles in that obstacle and produces a shower of particles, gamma rays, and x-rays.
Image credit Francisco Barradas Solas
I’m simplifying all of this, of course; things are always more complex than meets the eye. But given the steady decrease in numbers for a good 3 or more cycles now (with considerable fluctuation for several cycles before that), I will be surprised if, at some time in the next few cycles, we do not enter an extended minimum, even if only of moderate depth. And it really isn’t a matter of “if,” but of when. Many variable star astronomers (and that’s what I studied in school — spotted variables, no less) consider that the Sun is at the very least borderline variable; some consider it outrightly so. I tend to fall in the latter camp; it all depends on the percentage of variability, and we are only now obtaining the kind of data we need to determine that. But it doesn’t actually take much.
So things are picking up steam, and after many years of my talks, blog posts, etc., I am finally no longer the only person in the room standing up and saying, “Hey, folks, something interesting is going on here.” What’s going to happen next? I can’t say for sure. But it definitely bears watching. I’ll keep you posted as things develop, to the best of my ability.
Addendum from Old Uncle Lar:
I asked Steph to work this up from several on-line discussions she and I were a party to as well as a recent general observation from many sources that sunspot activity was way down from previous levels. I will endeavor to badger her into further developments as they occur.
Since I am also her business advisor I am compelled to mention that A Very UnCONventional Christmas, book three of the Division One series, will be available for pre-order on June 13 and sale on July 11. We expect to have print copies from a pre-production run available at Libertycon as well. Hope to see many of you there.